Exogenic carbon system

Based on the hrst simplihcation listed above, the exogenic cycles of carbon and sulfur are regarded as closed systems. As such, the bulk isotopic composition of average exogenic carbon and sulfur do not vary through time. We can write a rate equation for the rate of change in (mass X isotopic composition) of each reservoir in Figure 14 to reflect this isotope mass balance. For example ... 

Abstract Neurotransmission in the nervous system is initiated at presynaptic terminals by fusion of synaptic vesicles with the plasma membrane and subsequent exocytic release of chemical transmitters. Currently, there are multiple methods to detect neurotransmitter release from nerve terminals, each with their own particular advantages and disadvantages. For instance, most commonly employed methods monitor actions of released chemical substances on postsynaptic receptors or artificial substrates such as carbon libers. These methods are closest to the physiological setting because they have a rapid time resolution and they measure the action of the endogenous neurotransmitters rather than the signals emitted by exogenous probes. However, postsynaptic receptors only indirectly report neurotransmitter release in a form modified by the properties of receptors themselves, which are often nonlinear detectors of released substances. Alternatively, released chemical substances... 

Because sedimentary carbonates represent primarily chemical and biochemical precipitates from seawater, and because they make up 20% of the common sedimentary rock record, these rock types have been particularly good sources of chemical and mineralogical data for interpretation of the secular and cyclic evolution of the Earth s surface environment. This carbonate rock record as a function of geological age is now explored as are age trends in other rock types and sediment properties. With this information as background material, we can then discuss what these relationships tell us about the history of carbonates and the exogenic system throughout geologic dme. 

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