Sr/Ca and Mg/Ca ratios in polygenetic carbonate allochems from a Michigan marl lake

Rapid accumulation of CaCO3 is occurring in Littlefield Lake, a marl lake located in central Michigan. The sediment, which is 95% CaCO3, primarily consists of eight different genetic groups of carbonate allochems. These include calcite muds, sands, algal oncoids and Chara encrustations, as well as the dominant aragonitic gastropods Valvota tricarinota. Gyraulus deflectus and Amnicola integra. and the dominant aragonitic pelecypod Sphaerium partumeium. Samples of each of these groups were analyzed for Ca, Sr and Mg. Molar Mg/Ca ratios are primarily controlled by allochem mineralogy, with calcitic forms having Mg/Ca ratios 5-10 times larger than aragonitic (shelled) forms. The Sr/Ca ratios are primarily controlled by biochemical fractionation, and are significantly lower than Sr/Ca ratios of inorganically precipitated aragonite from other settings. Partition coefficients were determined for both Sr and Mg for each carbonate allochem group and, based on comparisons with results reported by other workers, the partition coefficients determined here are generally considered `typical' or representative values for biogeneous freshwater carbonates. An analysis of variance of the data indicates that most genera and species of carbonate-secreting organisms in marl lakes have highly characteristic Sr/Ca and Mg/Ca ratios. These ratios can potentially serve as geochemical tracers in future investigations of lacustrine carbonate diagenesis. Both Sr and Mg are influenced by grain size and/or surface area, probably due to the presence of these elements in non-lattice-held (exchangeable) positions.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24453/1/0000727.pd

The Unseen Face of E-Business Project Development

The purpose of this paper is intent on identify and analyze the unseen factors of successful or failure of e-business project development. The IT managers must take into account both all costs involved in e-business development and all phases (analysis, design, testing, implementation, maintenance and operation) according to principle of project management for software/systems life cycle development. There are many solutions to exceed these factors of failure among could be counted outsourcing, a good project management, involvement of senior management, a real cost estimation etc.Zadanie pt. „Digitalizacja i udostępnienie w Cyfrowym Repozytorium Uniwersytetu Łódzkiego kolekcji czasopism naukowych wydawanych przez Uniwersytet Łódzki” nr 885/P-DUN/2014 zostało dofinansowane ze środków MNiSW w ramach działalności upowszechniającej nauk

The development of space-pointing device "Airtouch"

There are many pointing input device information into the computer, the most common of which are a computer mouse and the touchpad on a laptop. However, they have their drawbacks: we must keep in hand the mouse to use it. Touchpad also does have a limited scope. We offer take out touchpad beyond the classical touchpad device. To this end, we propose to use an accelerometer and a gyroscope, attached to the finger, and a microcontroller with a wireless communication module and power element on the wrist. For competitive devices with similar device should differ ease, accuracy, and be affordable