Nightside Auroral Electrons at Mars: Upstream Drivers and Ionospheric Impact

International audienceDiscrete aurorae have been observed at Mars by multiple spacecraft, including Mars Express, Mars Atmosphere and Volatile EvolutioN (MAVEN), and most recently the United Arab Emirates Hope spacecraft. Meanwhile, there have been studies on the source particles responsible for producing these detectable aurorae (termed "auroral electrons"). By utilizing empirical criteria to select auroral electrons established by Xu et al. (2022, https://doi.org/10.1029/2022GL097757), we conduct statistical analyses of the impact of upstream drivers on the occurrence rate and fluxes of auroral electrons. We find the occurrence rate increases with upstream dynamic pressure and weakly depends on the interplanetary magnetic field strength. Meanwhile, the integrated auroral electron flux somewhat decreases with increasing upstream drivers. Auroral electron precipitation also occurs more frequently and is more intense over regions of strong crustal fields compared to weak crustal fields. Aside from emissions, auroral electrons are expected to cause significant impact ionization and enhance the plasma density locally. In this study, we also quantify the nightside ionospheric impact of auroral electron precipitation, specifically the thermal ion (O+, O2+, and CO2+) density enhancement, with MAVEN observations. Our results show that the ion density is increased by up to an order of magnitude at low altitudes. The crustal effects on ion density profiles for nominal electron and auroral electron precipitation are also discussed

Association of RNA Biosignatures With Bacterial Infections in Febrile Infants Aged 60 Days or Younger

ImportanceYoung febrile infants are at substantial risk of serious bacterial infections; however, the current culture-based diagnosis has limitations. Analysis of host expression patterns ("RNA biosignatures") in response to infections may provide an alternative diagnostic approach.ObjectiveTo assess whether RNA biosignatures can distinguish febrile infants aged 60 days or younger with and without serious bacterial infections.Design, setting, and participantsProspective observational study involving a convenience sample of febrile infants 60 days or younger evaluated for fever (temperature >38° C) in 22 emergency departments from December 2008 to December 2010 who underwent laboratory evaluations including blood cultures. A random sample of infants with and without bacterial infections was selected for RNA biosignature analysis. Afebrile healthy infants served as controls. Blood samples were collected for cultures and RNA biosignatures. Bioinformatics tools were applied to define RNA biosignatures to classify febrile infants by infection type.ExposureRNA biosignatures compared with cultures for discriminating febrile infants with and without bacterial infections and infants with bacteremia from those without bacterial infections.Main outcomes and measuresBacterial infection confirmed by culture. Performance of RNA biosignatures was compared with routine laboratory screening tests and Yale Observation Scale (YOS) scores.ResultsOf 1883 febrile infants (median age, 37 days; 55.7% boys), RNA biosignatures were measured in 279 randomly selected infants (89 with bacterial infections-including 32 with bacteremia and 15 with urinary tract infections-and 190 without bacterial infections), and 19 afebrile healthy infants. Sixty-six classifier genes were identified that distinguished infants with and without bacterial infections in the test set with 87% (95% CI, 73%-95%) sensitivity and 89% (95% CI, 81%-93%) specificity. Ten classifier genes distinguished infants with bacteremia from those without bacterial infections in the test set with 94% (95% CI, 70%-100%) sensitivity and 95% (95% CI, 88%-98%) specificity. The incremental C statistic for the RNA biosignatures over the YOS score was 0.37 (95% CI, 0.30-0.43).Conclusions and relevanceIn this preliminary study, RNA biosignatures were defined to distinguish febrile infants aged 60 days or younger with vs without bacterial infections. Further research with larger populations is needed to refine and validate the estimates of test accuracy and to assess the clinical utility of RNA biosignatures in practice

Epidemiology of Bacteremia in Febrile Infants Aged 60 Days and Younger

Study objectiveTo describe the current epidemiology of bacteremia in febrile infants 60 days of age and younger in the Pediatric Emergency Care Applied Research Network (PECARN).MethodsWe conducted a planned secondary analysis of a prospective observational study of febrile infants 60 days of age and younger presenting to any of 26 PECARN emergency departments (2008 to 2013) who had blood cultures obtained. We excluded infants with significant comorbidities or critically ill appearance. The primary outcome was prevalence of bacteremia.ResultsOf 7,335 screened infants, 4,778 (65.1%) had blood cultures and were enrolled. Of these patients, 84 had bacteremia (1.8%; 95% confidence interval [CI] 1.4% to 2.2%). The prevalence of bacteremia in infants aged 28 days or younger (47/1,515) was 3.1% (95% CI 2.3% to 4.1%); in infants aged 29 to 60 days (37/3,246), 1.1% (95% CI 0.8% to 1.6%). Prevalence differed by week of age for infants 28 days of age and younger (0 to 7 days: 4/156, 2.6%; 8 to 14 days: 19/356, 5.3%; 15 to 21 days: 15/449, 3.3%; and 22 to 28 days: 9/554, 1.6%). The most common pathogens were Escherichia coli (39.3%; 95% CI 29.5% to 50.0%) and group B streptococcus (23.8%; 95% CI 16.0% to 33.9%). Bacterial meningitis occurred in 19 of 1,515 infants 28 days of age and younger (1.3%; 95% CI 0.8% to 2.0%) and 5 of 3,246 infants aged 29 to 60 days (0.2%; 95% CI 0.1% to 0.4%). Of 84 infants with bacteremia, 36 (42.9%; 95% CI 32.8% to 53.5%) had urinary tract infections (E coli 83%); 11 (13.1%; 95% CI 7.5% to 21.9%) had bacterial meningitis.ConclusionThe prevalence of bacteremia and meningitis among febrile infants 28 days of age and younger is high and exceeds that observed in infants aged 29 to 60 days. E coli and group B streptococcus are the most common bacterial pathogens

Epidemiology of Bacteremia in Febrile Infants Aged 60 Days and Younger

Study objectiveTo describe the current epidemiology of bacteremia in febrile infants 60 days of age and younger in the Pediatric Emergency Care Applied Research Network (PECARN).MethodsWe conducted a planned secondary analysis of a prospective observational study of febrile infants 60 days of age and younger presenting to any of 26 PECARN emergency departments (2008 to 2013) who had blood cultures obtained. We excluded infants with significant comorbidities or critically ill appearance. The primary outcome was prevalence of bacteremia.ResultsOf 7,335 screened infants, 4,778 (65.1%) had blood cultures and were enrolled. Of these patients, 84 had bacteremia (1.8%; 95% confidence interval [CI] 1.4% to 2.2%). The prevalence of bacteremia in infants aged 28 days or younger (47/1,515) was 3.1% (95% CI 2.3% to 4.1%); in infants aged 29 to 60 days (37/3,246), 1.1% (95% CI 0.8% to 1.6%). Prevalence differed by week of age for infants 28 days of age and younger (0 to 7 days: 4/156, 2.6%; 8 to 14 days: 19/356, 5.3%; 15 to 21 days: 15/449, 3.3%; and 22 to 28 days: 9/554, 1.6%). The most common pathogens were Escherichia coli (39.3%; 95% CI 29.5% to 50.0%) and group B streptococcus (23.8%; 95% CI 16.0% to 33.9%). Bacterial meningitis occurred in 19 of 1,515 infants 28 days of age and younger (1.3%; 95% CI 0.8% to 2.0%) and 5 of 3,246 infants aged 29 to 60 days (0.2%; 95% CI 0.1% to 0.4%). Of 84 infants with bacteremia, 36 (42.9%; 95% CI 32.8% to 53.5%) had urinary tract infections (E coli 83%); 11 (13.1%; 95% CI 7.5% to 21.9%) had bacterial meningitis.ConclusionThe prevalence of bacteremia and meningitis among febrile infants 28 days of age and younger is high and exceeds that observed in infants aged 29 to 60 days. E coli and group B streptococcus are the most common bacterial pathogens