Experimental Studies of Cavity and Core Flow Interactions With Application to Ultra-Compact Combustors

Reducing the weight and decreasing pressure losses of aviation gas turbine engines improves the thrust-to-weight ratio and improves efficiency. In ultra-compact combustors (UCC), engine length is reduced and pressure losses are decreased by merging a combustor with adjacent components using a systems engineering approach. High-pressure turbine inlet vanes can be placed in a combustor to form a UCC. In this work, experiments were performed to understand the performance and associated physics within a UCC. Experiments were performed using a combustor operating at pressures in the range of 520–1030 kPa (75–150 psia) and inlet temperature equal to 480–620 K (865 R–1120 R). The primary reaction zone is in a single trapped-vortex cavity where the equivalence ratio was varied from 0.7 to 1.8. Combustion efficiencies and NO[subscript x] emissions were measured and exit temperature profiles were obtained for various air loadings, cavity equivalence ratios, and configurations with and without representative turbine inlet vanes. A combined diffuser-flameholder (CDF) was used to study the interaction of cavity and core flows. Discrete jets of air immediately above the cavity result in the highest combustion efficiencies. The air jets reinforce the vortex structure within the cavity, as confirmed through coherent structure velocimetry of high-speed images. The combustor exit temperature profile is peaked away from the cavity when a CDF is used. Testing of a CDF with vanes showed that combustion efficiencies greater than 99.5% are possible for 0.8 ≤ Φ[subscript cavity] ≤ 1.8. Temperature profiles at the exit of the UCC with vanes agreed within 10% of the average value. Exit-averaged emission indices of NO[subscript x] ranged from 3.5 to 6.5 g/kg[subscript fuel] for all test conditions. Increasing the air loading enabled greater mass flow rates of fuel with equivalent combustion efficiencies. This corresponds to increased vortex strength within the cavity due to the greater momentum of the air driver jets

Observations at Sea Level and Altitude on Basal MetabolicRate and Related Cardio-Pulmonary Functions

Basal metabolic rate, BMR, was measured at sea level and at altitude in 5 non-athletic males, two non-athletic females and 6 champion runners. Related measurements included pulmonary minute volume, heart rate, respiratory frequency, respiratory quotient and blood pressure. There was a wide variation in individual responses. Basal metabolic rate increased in all: the range was from a few percent to as much as 50%. The two females spent 25 days at 3,800 m followed by 19 days at 3,090 m; in the latter period, BMR of one of them approached the control level. There were individual patterns of response in BMR, pulmonary minute volume and heart rate but no pat­tern could be related to sex, age or physical activity. Pulmonary minute volume was elevated throughout the altitude stay, generally involving increases both in tidal volume and respiratory frequency. The breathing pattern was much more variable at altitude than at sea level indicated by a greater stan­dard deviation of respiratory frequency. Our findings, viewed in the light of other studies, indicate that large increase in BMR and smaller changes inheart rate and blood pressure are transitory. Eventually BMR returns to oralmost to sea level values, heart rate and blood pressure can adjust to sea level values even at 5,300 m and only pulmonary ventilation remains high

Genomic evidence for the evolution of Streptococcus equi : host restriction, increased virulence, and genetic exchange with human pathogens

The continued evolution of bacterial pathogens has major implications for both human and animal disease, but the exchange of genetic material between host-restricted pathogens is rarely considered. Streptococcus equi subspecies equi (S. equi) is a host-restricted pathogen of horses that has evolved from the zoonotic pathogen Streptococcus equi subspecies zooepidemicus (S. zooepidemicus). These pathogens share approximately 80% genome sequence identity with the important human pathogen Streptococcus pyogenes. We sequenced and compared the genomes of S. equi 4047 and S. zooepidemicus H70 and screened S. equi and S. zooepidemicus strains from around the world to uncover evidence of the genetic events that have shaped the evolution of the S. equi genome and led to its emergence as a host-restricted pathogen. Our analysis provides evidence of functional loss due to mutation and deletion, coupled with pathogenic specialization through the acquisition of bacteriophage encoding a phospholipase A(2) toxin, and four superantigens, and an integrative conjugative element carrying a novel iron acquisition system with similarity to the high pathogenicity island of Yersinia pestis. We also highlight that S. equi, S. zooepidemicus, and S. pyogenes share a common phage pool that enhances cross-species pathogen evolution. We conclude that the complex interplay of functional loss, pathogenic specialization, and genetic exchange between S. equi, S. zooepidemicus, and S. pyogenes continues to influence the evolution of these important streptococci.Publisher PDFPeer reviewe

Corrigendum to ‘Panton-Valentine Leucocidin (PVL) Staphylococcus aureus a position statement from the International Society of Chemotherapy’ [International Journal of Antimicrobial Agents 51/1 (2018) 16-25](S0924857917303941)(10.1016/j.ijantimicag.2017.11.002)

The authors regret that the author name Silvano Esposito was published incorrectly. The authors would like to apologise for any inconvenience caused