11When dealing with Atmospheric Boundary Layer (ABL) simulations, commer-

Summary Lycophytes are the earliest diverging extant lineage of vascular plants, sister to all other vascular plants. Given that most species are adapted to ever‐wet environments, it has been hypothesized that lycophytes, and by extension the common ancestor of all vascular plants, have few adaptations to drought. We investigated the responses to drought of key fitness‐related traits such as stomatal regulation, shoot hydraulic conductance (Kshoot) and stem xylem embolism resistance in Selaginella haematodes and S. pulcherrima, both native to tropical understory. During drought stomata in both species were found to close before declines in Kshoot, with a 50% loss of Kshoot occurring at −1.7 and −2.5 MPa in S. haematodes and S. pulcherrima, respectively. Direct observational methods revealed that the xylem of both species was resistant to embolism formation, with 50% of embolized xylem area occurring at −3.0 and −4.6 MPa in S. haematodes and S. pulcherrima, respectively. X‐ray microcomputed tomography images of stems revealed that the decline in Kshoot occurred with the formation of an air‐filled lacuna, disconnecting the central vascular cylinder from the cortex. We propose that embolism‐resistant xylem and large capacitance, provided by collapsing inner cortical cells, is essential for Selaginella survival during water deficit.

The use of multi-stage centrifugal compressors carries out a leading role in oil and gas process applications. Green operation and market competitiveness require the use of low-cost reliable compression units with high efficiencies and wide operating range. A methodology is presented for the design optimization of multi-stage centrifugal compressors with prediction of the compressor map and estimation of the uncertainty limits. A one-dimensional (1D) design tool has been developed that automatically generates a multi-stage radial compressor satisfying the target machine requirements based on a few input parameters. The compressor performance map is then assessed using the method proposed by Casey-Robinson [1], and the approach developed by Al-Busaidi-Pilidis [2]. The off-design performance method relies on empirical correlations calibrated on the performance maps of many single-stage centrifugal compressors. An uncertainty quantification study on the predicted performance maps was conducted using Monte Carlo method (MCM) and generalized Polynomial Chaos Expansion (gPCE). Finally, the design procedure has been coupled to an in-house optimizer based on evolutionary algorithms. The complete design procedure has been applied to a multi-stage industrial compressor test case. A multi-objective optimization of a multi-stage industrial compressor has been performed targeting maximum compressor efficiency and flow range. The results of the optimization show the existence of optimum compressor architectures and how the Pareto fronts evolve depending on the number of stages and shafts.