Analysis of a carbon dioxide transcritical power cycle using a low temperature source

A detailed analysis of a carbon dioxide transcritical power cycle using an industrial low-grade stream of process gases as its heat source is presented. The methodology is divided in four steps: energy analysis, exergy analysis, finite size thermodynamics and calculation of the heat exchangers' surface. The results have been calculated for fixed temperature and mass flow rate of the heat source, fixed maximum and minimum temperatures in the cycle and a fixed sink temperature by varying the high pressure of the cycle and its net power output. The main results show the existence of an optimum high pressure for each of the four steps; in the first two steps, the optimum pressure maximises the thermal or exergetic efficiency while in the last two steps it minimises the product UA or the heat exchangers' surface. These high pressures are very similar for the energy and exergy analyses. The last two steps also have nearly identical optimizing high pressures that are significantly lower that the ones for the first two steps. In addition, the results show that the augmentation of the net power output produced from the limited energy source has no influence on the results of the energy analysis, decreases the exergetic efficiency and increases the heat exchangers' surface. Changing the net power output has no significant impact on the high pressures optimizing each of the four steps.Waste heat Energy analysis Exergy analysis Finite size thermodynamics Heat exchanger surface Optimization

Strong, reliable and precise synaptic connections between thalamic relay cells and neurones of the nucleus reticularis in juvenile rats

The thalamic reticular nucleus (nRT) is composed entirely of GABAergic inhibitory neurones that receive input from pyramidal cortical neurones and excitatory relay cells of the ventrobasal complex of the thalamus (VB). It plays a major role in the synchrony of thalamic networks, yet the synaptic connections it receives from VB cells have never been fully physiologically characterised. Here, whole-cell current-clamp recordings were obtained from 22 synaptically connected VB-nRT cell pairs in slices of juvenile (P14–20) rats. At 34–36 °C, single presynaptic APs evoked unitary EPSPs in nRT cells with a peak amplitude of 7.4 ± 1.5 mV (mean ± s.e.m.) and a decay time constant of 15.1 ± 0.9 ms. Only four out of 22 pairs showed transmission failures at a mean rate of 6.8 ± 1.1 %. An NMDA receptor (NMDAR)-mediated component was significant at rest and subsequent EPSPs in a train were depressed. Only one out of 14 pairs tested was reciprocally connected; the observed IPSPs in the VB cell had a peak amplitude of 0.8 mV and were completely abolished in the presence of 10 μm bicuculline. Thus, synaptic connections from VB cells to nRT neurones are mainly ‘drivers’, while a small subset of cells form closed disynaptic loops