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In this work, three commercially available Membrane Electrode Assemblies (MEAs) from Advent Technology Inc. and Danish Power Systems, developed for a use in High Temperature Proton Exchange Membrane Fuel Cell (HT-PEMFC), were tested under various Operating Conditions (OCs): over-stoichiometry of hydrogen gas (1.05, 1.2, 1.35), over-stoichiometry of air gas (1.5, 2, 2.5), gas oxidant (O2 or air) and temperature (140 °C, 160 °C, 180 °C). For each set of operating conditions, a polarization curve (V–I curve) was performed. A semi-empirical and macroscopic (0D) model of the fuel cell voltage was established in steady state conditions in order to model some of these experimental data. The proposed parameterization approach for this model (called here the "multi-VI" approach) is based on the sensitivity to the operating conditions specific to each involved physicochemical phenomenon. According to this method, only one set of parameters is used in order to model all the experimental curves (optimization is performed simultaneously on all curves). A model depending on air over-stoichiometry was developed. The main objective is to validate a simple (0D) and fast-running model that considers the impact of air over-stoichiometry on cell voltage regarding all commercially available MEAs. The obtained results are satisfying with AdventPBI MEA and Danish Power Systems MEA: an average error less than 1.5% and a maximum error around 15% between modelled and measured voltages with only nine parameters to identify. However, the model was not as adapted to Advent TPS® MEA: average error and maximum error around 4% and 21%, respectively. Most of the obtained parameters appear consistent regardless of the OCs. The predictability of the model was also validated in the explored domain during the sensibility study with an interesting accuracy for 27 OCs after being trained on only nine curves. This is attractive for industrial application, since it reduces the number of experiments, hence the cost of model development, and is potentially applicable to all commercial HT-PEMFC MEAs. [ABSTRACT FROM AUTHOR]

High-Temperature Proton Exchange Membrane Fuel Cell constant current ageing tests highlighted that the characterizations used to monitor the state of health of single cells could be potentially degrading. An experimental campaign to analyze potential degradation due to polarization curves was carried out. More exactly, four methodologies to generate a polarization curve including Electrochemical Impedance Spectroscopies (EIS) were cycled 30 times. The tested single cells were based on a commercial PBI Membrane Electrodes Assembly (MEA) with an active surface of 45 cm2 (BASF Celtec®-P 1100 type). Before the first cycling test and after the last cycling one, complete characterizations, composed by a voltammetry and a polarization curve including EIS, were performed. The results show that one of the MEA has a voltage which increased for one of the four methods to obtain the polarization curve. This growth is linked to a decrease of ohmic losses: in an unexpected way, it could be considered as a way to improve the break-in period. Similarly, the monitoring of CO2 emission (as corrosion has been suspected to be involved at high voltage, i.e. low current density) confirms the potential degradation of the electrodes during the measurement of the polarization curve.

Introduction: Noncombat-related hand injuries are common in current theatres of operations. Crushing is one of the most frequent mechanisms that may cause traumatic amputations of digits. In the military setting, management of these digital amputations is challenging regarding limitation in microsurgical means in medical treatment facilities and aeromedical evacuation delays out of the combat zone. Methods: Two cases of digital replantation performed in French forward surgical units are described. The first case was a complete distal amputation of the medius which was successfully replanted in the operating theatre of an aircraft carrier. No complication was observed after evacuation. Functional and aesthetic results were excellent. The second case was a ring finger avulsion revascularized in a role 2 facility in Central African Republic. Unfortunately, revascularization failed due to arterial thrombosis during evacuation. Results: Digital, hand or more proximal upper extremity replantation may be considered for isolated amputations due to work-related accidents within the combat zone. For a surgeon trained to microsurgery, a microsurgical set and magnification loupes enable to attempt such procedures in austere conditions. Discussion: The authors propose an algorithm of management in the field according to the type and level of amputation.

Introduction: The development of damage control orthopedics (DCO) procedures has led to the development of temporary unicortical external fixators (TUEFs) intended to limit deep infectious complications and facilitate early conversion to internal fixation. Methods: A retrospective study was conducted in two French military trauma centers, including on patients being treated for tibial fractures with a TUEF (UNYCO® − Orthofix®) followed by an early conversion to intramedullary nailing. Results: Eleven patients with an average age of 41 were included between September 2015 and June 2017. A total of 12 TUEFs were implanted for one closed fracture and 11 open fractures, including one type I, eight types II, and two Gustilo types IIIB. The indication of DCO was related to hemodynamic instability in three cases, to the severity of soft tissue lesions in eight cases, and to the context of treatment in one case. The conversion to IM nailing was made after an average of 7.6 days. No significant loss of reduction was observed until internal osteosynthesis, which was performed with “fixator in place” in ten cases. The coverage of Gustilo type III injuries was performed by free flap transfers at the same time as IM nailing. All the patients were reviewed with an average follow-up of 16.5 months. Bone union was achieved in all cases. Two IM nailing dynamizations were carried out, but no bone grafting was required. Two cases of pandiaphysitis were observed and treated without functional complications. Discussion: Despite a limited number of patients, this study demonstrates the reliability of the TUEF to maintain the reduction of tibial fractures and facilitate early conversion to IM nailing. Unicortical fixation does not prevent septic complications related to the severity of soft tissue injuries.