Evaluation of methods for characterizing the fine particulate matter emissions from aircraft and other diffusion flame combustion aerosol sources.

The U. S. Environmental Protection Agency in collaboration with the U. S. Air Force Arnold Engineering Development Complex conducted the VAriable Response In Aircraft nvPM Testing (VARIAnT) 3 and 4 test campaigns to compare nonvolatile particulate matter (nvPM) emissions measurements from a variety of diffusion flame combustion aerosol sources (DFCASs), including a Cummins diesel engine, a diesel powered generator, two gas turbine start carts, a J85-GE-5 turbojet engine burning multiple fuels, and a Mini-CAST soot generator. The VARIAnT research program was devised to understand reported variability in the ARP6320A sampling system nvPM measurements. The VARIAnT research program has conducted four test campaigns to date with the VARIAnT 3 and 4 campaigns devoted to: (1) assessing the response of three different black carbon mass analyzers to particles of different size, morphology, and chemical composition; (2) characterizing the particles generated by 6 different combustion sources according to morphology, effective density, and chemical composition; and (3) assessing any significant difference between black carbon as determined by the 3 mass analyzers and the total PM determined via other techniques. Results from VARIAnT 3 and 4 campaigns revealed agreement of about 20% between the Micro-Soot Sensor, the Cavity Attenuated Phase Shift (CAPS PMSSA) monitor and the thermal-optical reference method for elemental carbon (EC) mass, independent of the calibration source used. For the LII-300, the measured mass concentrations in VARIAnT 3 fall within 18% and in VARIAnT 4 fall within 27% of the reference EC mass concentration when calibrated on a combustor rig in VARIAnT 3 and on an LGT-60 start cart in VARIAnT 4, respectively. It was also found that the three mass instrument types (MSS, CAPS PMSSA, and LII-300) can exhibit different BC to reference EC ratios depending on the emission source that appear to correlate to particle geometric mean mobility diameter, morphology, or some other parameter associated with particle geometric mean diameter (GMD) with the LII-300 showing a slightly stronger apparent trend with GMD. Systematic differences in LII-300 measured mass concentrations have been reduced by calibrating with a turbine combustion as a particle source (combustor or turbine engine). With respect to the particle size measurements, the sizing instruments (TSI SMPS, TSI EEPS, and Cambustion DMS 500) were found to be in general agreement in terms of size distributions and concentrations with some exceptions. Gravimetric measurements of the total aerosol mass produced by the various DFCAs differed from the reference EC, BC and integrated particle size distribution measured aerosol masses. The measurements of particle size distributions and single particle analysis performed using the miniSPLAT indicated the presence of larger particles (≳150 nm) having more compact morphologies, higher effective density, and a composition dominated by OC and containing ash. This increased large particle fraction is also associated with higher values of single scattering albedo measured by the CAPS PMSSA instrument and higher OC measurements. These measurements indicate gas turbine engine emissions can be a more heterogeneous mix of particle types beyond the original E-31 assumption that engine exit exhaust particles are mainly composed of black carbon.

The effects of chlorination, thickness, and moisture on glove donning efficiency.

Changing gloves more frequently is encouraged, more now than ever given the COVID-19 pandemic. When the donning process has moisture introduced, however, complications can arise, which consumes vital time. Most commonly, gloves undergo a chlorination treatment to reduce glove tack, allowing easier donning. To assess the effects of different chlorination strengths and glove thicknesses on donning, acrylonitrile butadiene gloves were manufactured at two different thicknesses (0.05 and 0.10 mm) with 4 different chlorination treatments: 0, 500, 1000 and 2000 ppm. Six participants were used to assess the time taken to don each of the glove sets with dry and wet hands (16 tests in total). Overall, the thicker gloves took longer to don, due to differences in the material stiffness hindering the donning process. The quickest performance from the chlorinated gloves was noted in the 1000 and 2000 ppm concentrations. Wet conditions also showed significant increases in the donning time.Practitioners Summary: The study was conducted based on the gaps identified in previous literature reviews which revealed the requirement for a greater understanding of glove donning process. It was found a stronger chlorination was detrimental when the hands were wet, but better when dry. Thicker gloves were also found to be detrimental. Abbreviations: PPE: personal protective equipment; NBR: acrylonitrile butadiene rubber; NRL: natural rubber latex; EN: European standards; s: seconds; Ts: tensile strength; Fb: force at break; T: thickness; Eb: elongation at break; HSD: honest significant difference; FTIR: Fourier transform infrared; covid-19: coronavirus disease 2019.

"Let's get physical": advantages of a physical model over 3D computer models and textbooks in learning imaging anatomy.

Three-dimensional (3D) information plays an important part in medical and veterinary education. Appreciating complex 3D spatial relationships requires a strong foundational understanding of anatomy and mental 3D visualization skills. Novel learning resources have been introduced to anatomy training to achieve this. Objective evaluation of their comparative efficacies remains scarce in the literature. This study developed and evaluated the use of a physical model in demonstrating the complex spatial relationships of the equine foot. It was hypothesized that the newly developed physical model would be more effective for students to learn magnetic resonance imaging (MRI) anatomy of the foot than textbooks or computer-based 3D models. Third year veterinary medicine students were randomly assigned to one of three teaching aid groups (physical model; textbooks; 3D computer model). The comparative efficacies of the three teaching aids were assessed through students' abilities to identify anatomical structures on MR images. Overall mean MRI assessment scores were significantly higher in students utilizing the physical model (86.39%) compared with students using textbooks (62.61%) and the 3D computer model (63.68%) (P < 0.001), with no significant difference between the textbook and 3D computer model groups (P = 0.685). Student feedback was also more positive in the physical model group compared with both the textbook and 3D computer model groups. Our results suggest that physical models may hold a significant advantage over alternative learning resources in enhancing visuospatial and 3D understanding of complex anatomical architecture, and that 3D computer models have significant limitations with regards to 3D learning.

Altering n-3 to n-6 polyunsaturated fatty acid ratios affects prostaglandin production by ovine uterine endometrium.

Consumption of n-3 polyunsaturated fatty acids (PUFAs) is considered beneficial to health but effects on fertility remain uncertain. This study investigated the effect of n-3 PUFA supplementation on endometrial prostaglandin (PG) production. Ovine uterine endometrial cells were cultured to confluence in DMEM/F12 medium containing 10% foetal bovine serum. Stromal and epithelial cell populations were confirmed by immunocytochemistry. Cultures were supplemented with 0, 20 or 100 µM of α-linolenic acid (ALA), stearidonic acid (SDA), eicosapentaenoic acid (EPA) with lipopolysaccharide (LPS) at 0 and 0.1 µg/ml, or different combinations of EPA with arachidonic acid (AA) in serum-free medium for 24h. PGs were quantified using radioimmunoassay and PG-endoperoxide synthase (PTGS) isoforms, PGE and PGF synthase (microsomal PGES1 and PGFS) mRNAs by qPCR. LPS increased PGE2 production significantly without changing PGF2α production, causing increased PGE2:PGF2α ratios. ALA and SDA increased PGE2, PGF2α and PGE2:PGF2α ratios (P<0.05-0.01) while EPA alone did not affect PG generation. AA significantly stimulated PTGS1 and PTGS2 mRNA expression and PGE2 and PGF2α production (P<0.01). The stimulatory effect of AA was attenuated by up to 80% (P<0.05) when AA was combined with EPA. The PGE2:PGF2α ratio was not affected by AA or EPA alone, but increased when these two PUFAs were combined (P<0.05). SDA and EPA decreased PTGS1 mRNA expression (P<0.05) but did not alter PTGS2 expression. EPA and AA up-regulated mPGES1 expression (P<0.05) without affecting PGFS expression. Since AA is preferentially incorporated in uterine endometrium to produce 2-series PGs, alteration of PG production by EPA may affect many reproductive processes.