A comparison of the ecophysiological response on copper in Baltic clams from different populations in Europe

Differences in performance and bioaccumulation of copper, metallothionein-like protein (MTLP) levels and resistance in Baltic clams, Macoma balthica, from Arctic, subarctic and temperate areas were determined during a stress period caused by starvation and exposure to copper. Although the conditions at the start were different, the losses of weight and mortality rates were in general comparable in clams from all areas. In contrast to expectation, the accumulation of copper in (sub)Arctic clams was much faster than in temperate specimens, whereas the level of MTLP in all populations hardly increased. Copper was primarily accumulated in insoluble form: MTLP has in clams no major role in copper sequestration. It is suggested that the differences in copper accumulation rates between populations might be related to genetic (racial) differentiation. [KEYWORDS: bioaccumulation; metal; copper; metallothionein; stress sensitivity; bivalve; Macoma balthica; Arctic bivalve macoma-balthica; metallothionein-like proteins; metal exposure; genetic adaptations; arctic populations; aquatic animals; southern limit; trace-metals; bioaccumulation; sensitivity]

Capacity of a LoRaWAN Cell

International audienceIn this paper, we consider the problem of evaluating the capacity of a LoRaWAN cell. Previous analytical studies investigated LoRaWAN performance in terms of the Packet Delivery Ratio (PDR) given a number of devices around a gateway and its range. We improve the model for PDR by taking into consideration that the following two events are dependent: successful capture during a collision and successful frame decoding despite ambient noise. We consider a realistic traffic model in which all devices generate packets with the same inter-transmission times corresponding to the duty cycle limitation at the highest SF, regardless of the distance to the gateway. Based on the developed model, we optimize the Spreading Factor (SF) boundaries to even out PDR throughout the cell. We validate the analytical results with simulations, compare our model with previous work, and experimentally validate the hypothesis of Rayleigh fading for the LoRa channel. The important conclusion from our results is that a LoRa cell can handle a relatively large number of devices. We also show that there is practically no inter-SF interference (cross interference between transmissions with different SFs): interference from higher SFs comes from nodes located farther away, so they face greater attenuation and thus, they do not interfere with lower SF nodes