Evaluation of Work Efficiency in Structural Firefighters.

ABSTRACT: Langford, EL, Bergstrom, HC, Lanham, S, Eastman, AQ, Best, S, Ma, X, Mason, MR, and Abel, MG. Evaluation of work efficiency in structural firefighters. J Strength Cond Res 37(12): 2457-2466, 2023-To perform occupational tasks safely and effectively, firefighters (FF) must work quickly and consume air provided by the self-contained breathing apparatus (SCBA) efficiently. However, most literature only factors work rate into performance, neglecting the inherent time limitation imposed by the SCBA. The purpose of this article was to (a) evaluate the reliability and variability in a "work efficiency" (WE) performance metric reflective of both work rate and air consumption; (b) explore the relationship between WE and established measures of metabolic strain; and (c) identify fitness, anthropometric, and demographic correlates of WE. About 79 structural FF completed an air consumption drill while breathing through an SCBA. Self-paced work duration and air consumption were entered into the WE equation. A subsample of FF (n = 44) completed another randomized trial while breathing through a portable gas analyzer. Anthropometric and fitness data were collected separately. Correlations were performed between WE vs. fitness, anthropometric, demographic, and metabolic outcomes. Multiple linear regression was used to identify the strongest predictors of WE. WE was reliable (intraclass correlation coefficient = 0.71) and yielded inter-FF variability {0.79 ± 0.25 ([lb·in-2·min]-1) × 104; coefficient of variation = 31.6%}. WE was positively correlated to oxygen consumption (V̇O2) (L·minute-1, mL·kg-1·minute-1) and tidal volume and negatively correlated to V̇E/V̇O2 and respiratory frequency. Height, upper-body endurance, and aerobic endurance were identified as the strongest predictors of WE (adjusted R2 = 0.59, RMSE = 0.16). WE is a reliable and occupationally relevant method to assess FF performance because it accounts for work rate and air consumption. Firefighters may enhance WE through a training intervention focused on improving metabolic tolerance, upper-body endurance, and aerobic endurance.

Synthesis and calorimetric, spectroscopic, and structural characterization of isocyanide complexes of trialkylaluminum and tri-tert-butylgallium.

Addition of tert-butylisocyanide or 2,6-dimethylphenylisocyanide to a solution of trialkylaluminum or trialkylgallium results in formation of complexes R(3)M·C≡N(t)Bu (M = Al, R = Me (1), Et (2), (i)Bu (3), (t)Bu (4); M = Ga, R = (t)Bu (9)) or R(3)M·C≡N(2,6-Me(2)C(6)H(3)) (M = Al, R = Me (5), Et (6), (i)Bu (7), (t)Bu (8); M = Ga, R = (t)Bu (10)), respectively. Complexes 1, 4, 5, and 8-10 are isolated as solids, whereas the triethylaluminum and triisobutylaluminum adducts 2, 3, 6, and 7 are viscous oils. Complexes 1-10 were characterized by NMR ((1)H, (13)C) and IR spectroscopies, and the molecular structures of 4, 5, and 8-10 were also determined by X-ray crystallography. The frequency of the C≡N stretch of the isocyanide increased by 58-91 cm(-1) upon complexation, consistent with coordination of the isocyanide as a σ donor. Enthalpies of complex formation for 1-10 were determined by isothermal titration calorimetry. Enthalpy data suggest the following order of decreasing Lewis acidity: (t)Bu(3)Al ≫ (i)Bu(3)Al ≥ Me(3)Al ≈ Et(3)Al ≫ (t)Bu(3)Ga. In the absence of oxygen and protic reagents, the reported complexes do not undergo insertion or elimination reactions upon heating their benzene-d(6) solutions to 80 °C.

Aluminum alkoxide, amide and halide complexes supported by a bulky dipyrromethene ligand: synthesis, characterization, and preliminary ε-caprolactone polymerization activity.

Aluminum halide, alkoxide and amide complexes 2-6 of the form (N,N)AlX2-nYn (n = 0, 1 and (N,N) = 1,9-dimesityl-5-phenyldipyrromethene (1)) were synthesized and characterized by NMR spectroscopy and X-ray crystallography. The in situ generated lithium salt of dipyrromethene 1 was reacted with AlX3 to afford aluminum halide complexes (N,N)AlX2 (X = Cl (2), I (3)) which were isolated as dichroic crystals. Salt metathesis reactions were employed to produce alkoxide complexes (N,N)Al(Cl)(O(t)Bu) (4) and (N,N)Al(O(t)Bu)2 (5) from compound 2. The dimethylamide complex (N,N)Al(NMe2)2 (6) was prepared by reaction of dipyrromethene 1 with [Al(NMe2)3]2. Crystallographic data revealed that the dipyrromethene is non-planar when bulky coligands are present as in compounds 3-6, while in the dichloride complex 2 the dipyrromethene is planar. Halide complexes 2 and 3 reacted with adventitious moisture in toluene to afford crystalline acid-base adducts (N,N)H·HX, (X = Cl (7), I (8)), which adopted structures reminiscent of anion receptors. Alkoxide and dimethylamide complexes 5 and 6 were also applied as precatalysts for the ring-opening polymerization of ε-caprolactone and preliminary results are reported.

Synthesis and Characterization of Dimeric, Trimeric, and Tetrameric Gallophosphonates and Gallophosphates.

THF/toluene solutions of phosphonic or phosphoric acids were reacted with (t)Bu(3)Ga at low temperature to yield the cyclic dimers [(t)Bu(2)GaO(2)P(OH)R](2) (R = Ph, Me, (t)Bu, H, OH; 1-5). Poor crystallinity and variable thermal stabilities of 1-5 necessitated derivatization with Me(3)SiNMe(2) to yield [(t)Bu(2)GaO(2)P(OSiMe(3))R](2) (R = Ph, Me, (t)Bu, H, OSiMe(3); 6-10), which were more amenable to purification and characterization. In solution, trans isomers were predominant for 6 and 7 at ambient temperature, whereas the cis isomer of 8 was predominant. NMR spectroscopy demonstrated cis-trans interconversion for 6-8 and crossover experiments showed interconversion to occur by, or be accompanied with, an intermolecular exchange process. Thermolysis of 3 in refluxing toluene yielded the cluster [((t)BuGa)(2)((t)Bu(2)Ga)(O(3)P(t)Bu)(2){O(2)P(OH)(t)Bu}] (11), which was converted to [((t)BuGa)(2)((t)Bu(2)Ga)(O(3)P(t)Bu)(2){O(2)P(OSiMe(3))(t)Bu}] (12) with Me(3)SiNMe(2). Thermolysis of 1-3 in refluxing diglyme, or solid-state pyrolysis at 250 degrees C in vacuo, yielded [(t)BuGaO(3)PR](4) (R = Ph, (t)Bu, Me; 13-15). The gallophosphate [(t)BuGaO(3)P(OSiMe(3))](4) (16) was similarly obtained by reaction of (t)Bu(3)Ga with H(3)PO(4) in refluxing diglyme, followed by trimethylsilylation with Me(3)SiNMe(2). Compounds 13-16 possess cuboidal Ga(4)P(4)O(12) cores analogous to double-four-ring secondary building units in the gallophosphates cloverite, gallophosphate-A, and ULM-5. The thermal, hydrolytic, and oxidative stabilities of 13-16 are discussed, as are observed intermolecular exchange processes. In addition to characterization of 1-16 by multinuclear ((1)H, (13)C, (31)P) NMR spectroscopy, infrared spectroscopy, mass spectrometry, and elemental analysis, molecular structures for compounds 6, 8, 10, 12, 14, 15, and 16 were determined by X-ray crystallography.

Titanium and zirconium amido complexes ligated by 2,2'-Di(3-methylindolyl)methanes: synthesis, characterization, and ethylene polymerization activity.

2,2'-Di(3-methylindolyl)methanes (L(2)H(2)) are introduced as dianionic, bidentate ligands of reduced pi-donating ability. Four complexes of the type L(2)Ti(NEt(2))(2) and L(2)Zr(NEt(2))(2)(THF) have been synthesized and characterized by elemental analysis, NMR ((1)H, (13)C) spectroscopy, and X-ray crystallography. Structural data confirm the reduced pi-donating ability of the eta(1)-indolyl moiety compared to that of diethylamido. Preliminary catalytic activities of these group 4 complexes for the polymerization of ethylene are reported.

Remarkable room-temperature insertion of carbon monoxide into an aluminum-carbon bond of tri-tert-butylaluminum.

Room-temperature reaction of carbon monoxide with tri-tert-butylaluminum at atmospheric pressure yields the dimeric tert-butylacyl complex [tBu2AlC(O)tBu]2 (1). This unprecedented CO insertion into an aluminum-carbon bond is apparently made possible by the three-coordinate aluminum center in the tri-tert-butylaluminum starting material.

Hydroformylation of 1-hexene in supercritical carbon dioxide: characterization, activity, and regioselectivity studies.

The hydroformylation of alkenes is a major commercial process used for the production of oxygenated organic compounds. When the hydroformylation reaction is performed using a homogeneous catalyst, an organic or aqueous solvent is employed, and a significant effort must be expended to recover the catalyst so it can be recycled. Development of a selective heterogeneous catalyst would allow simplification of the process design in an integrated system that minimizes waste generation. Recent studies have shown that supercritical carbon dioxide (scCO2) as a reaction solvent offers optimal environmental performance and presents advantages for ease of product separation. In particular, we have considered the conversion of 1-hexene to heptanal using rhodium- and platinum-phosphine catalysts tethered to supports insoluble in scCO2 to demonstrate the advantages and to understand the limitations of a solid-catalyzed process. One of the historical limitations of supported catalysts is the inability to control product regioselectivity. To address this concern, we have developed tethered catalysts with phosphinated silica and controlled pore size MCM-41 and MCM-20 supports that provide improved regioselectivity and conversion relative to their nonporous equivalents. Platinum catalysts supported on MCM-type supports were the most regioselective whereas the analogous rhodium catalysts were the most active for hydroformylation of 1-hexene in scCO2.