Personal protective equipment impacts firefighters' anaerobic fitness.

BACKGROUND: Personal protective equipment (PPE) is vital for firefighters' safety and effectiveness during daily operations. However, concerns have emerged about its potential impact on firefighters' anaerobic fitness (AF), which is crucial for their operational readiness. The Physical Ability Test (PAT) is used to assess readiness, but there is inconsistency among fire departments regarding whether PAT is conducted with full PPE or regular exercise clothing. This variation in testing conditions may exacerbate the stress on firefighters' AF. AIMS: To analyse differences in firefighters' AF performance while wearing full PPE compared to regular exercise clothing. METHODS: We studied two cohorts totalling 62 firefighters from specific fire departments in South Florida. We conducted occupation-specific AF tests, including handgrip dynamometry (HG), vertical jump (VJ), Margaria-Kalamen (MK), and a 300-yard shuttle run (300YD), both with full PPE (WPPE) and without PPE (NPPE). We adjusted AF variables for body weight (e.g. NPPE) and occupational weight (e.g. WPPE) and used a repeated-measures design in Jamovi (P < 0.05). RESULTS: Wearing WPPE significantly reduced relative HG strength by 59%, VJ peak power by 11%, and MK mean power by 49%, while increased 300YD completion time by 18%. CONCLUSIONS: The study reveals that PPE substantially impairs firefighters' anaerobic performance during occupation-specific tests. This emphasizes the need for tailored AF training programs to support the anaerobic system and related performance while wearing PPE, acknowledging the significance of occupational specificity in assessing firefighters' fitness components.

Evaluation of a Ti-Base Alloy as Steam Cracking Reactor Material.

Low-coking reactor material technologies are key for improving the performance and sustainability of steam crackers. In an attempt to appraise the coking performance of an alternative Ti-base alloy during ethane steam cracking, an experimental study was performed in a jet stirred reactor under industrially relevant conditions using thermogravimetry (Tgasphase = 1173 K, Ptot = 0.1 MPa, XC2H6 = 70%, and dilution δ = 0.33 kgH2O/kgHC). Initially, a typical pretreatment used for Fe-Ni-Cr alloys was utilized and compared with a pretreatment at increased temperature, aiming at better surface oxidation and thus suppressing coke formation. The results revealed a decrease in coking rates upon high temperature pretreatment of the Ti-base alloy, however, its coking performance was significantly worse compared to the typically used Fe-Ni-Cr alloys, and carbon oxides formation increased by a factor of 30 or more. Moreover, the analyzed coupons showed crack propagation after coking/decoking and cooling down to ambient temperature. Scanning electron microscopy combined with energy-dispersive X-ray spectroscopy indicated that the prompt and unsystematic oxidation of the surface and bulk caused observable crack initiation and propagation due to alloy brittleness. Hence, the tested Ti-base alloy cannot be considered an industrially noteworthy steam cracking reactor alloy.

Effect of Long-Term High Temperature Oxidation on the Coking Behavior of Ni-Cr Superalloys.

The service time of an industrial cracker is strongly dependent on the long-term coking behavior and microstructure stability of the reactor coil alloy. Super alloys are known to withstand temperatures up to even 1400 K. In this work, several commercially available alloys have been first exposed to a long term oxidation at 1423 K for 500 h, so-called metallurgic aging. Subsequently, their coking behavior was evaluated in situ in a thermogravimetric setup under ethane steam cracking conditions (Tgasphase = 1173 K, Ptot = 0.1 MPa, XC2H6 = 70%, continuous addition of 41 ppmw S/HC of DMDS, dilution δ = 0.33 kgH2O/kgHC) and compared with their unaged coking behavior. The tested samples were also examined using scanning electron microscopy and energy diffractive X-ray for surface and cross-section analysis. The alloys characterized by increased Cr-Ni content or the addition of Al showed improved stability against bulk oxidation and anti-coking behavior after application of metallurgic aging due to the formation of more stable oxides on the top surface.

New perspectives on thiamine catalysis: from enzymic to biomimetic catalysis.

This paper is a brief review of the detailed mechanism of action of thiamine enzymes, based on metal complexes of bivalent transition and post-transition metals of model compounds, thiamine derivatives, synthesized and characterized with spectroscopic techniques and X-ray crystal structure determinations. It is proposed that the enzymatic reaction is initiated with a V conformation of thiamine pyrophosphate, imposed by the enzymic environment. Thiamine pyrophosphate is linked with the proteinic substrate through its pyrophosphate oxygens. In the course of the reaction, the formation of the "active aldehyde" intermediate imposes the S conformation to thiamine, while a bivalent metal ion may be linked through the N1' site of the molecule, at this stage. Finally, the immobilization of thiamine and derivatives on silica has a dramatic effect on the decarboxylation of pyruvic acid, reducing the time of its conversion to acetaldehyde from 330 minutes for the homogeneous system to less than 5 minutes in the heterogenous system.