Exhaust emission reduction for intermittent combustion aircraft engines

Three concepts for optimizing the performance, increasing the fuel economy, and reducing exhaust emission of the piston aircraft engine were investigated. High energy-multiple spark discharge and spark plug tip penetration, ultrasonic fuel vaporization, and variable valve timing were evaluated individually. Ultrasonic fuel vaporization did not demonstrate sufficient improvement in distribution to offset the performance loss caused by the additional manifold restriction. High energy ignition and revised spark plug tip location provided no change in performance or emissions. Variable valve timing provided some performance benefit; however, even greater performance improvement was obtained through induction system tuning which could be accomplished with far less complexity

Polarimetric Properties of the Crab Pulsar between 1.4 and 8.4 GHz

New polarimetric observations of the Crab pulsar at frequencies between 1.4 and 8.4 GHz are presented. Additional pulse components discovered in earlier observations (Moffett & Hankins 1996, astro-ph/9604163) are found to have high levels of linear polarization, even at 8.4 GHz. No abrupt sweeps in position angle are found within pulse components; however, the position angle and rotational phase of the interpulse do change dramatically between 1.4 and 4.9 GHz. The multi-frequency profile morphology and polarization properties indicate a non-standard origin of the emission. Several emission geometries are discussed, but the one favored locates sites of emission both near the pulsar surface and in the outer magnetosphere.Comment: 20 pages, 7 postscript figures, uses aaspp4 Latex style. To appear in Volume 522 of The Astrophysical Journa

Calibrating the projection factor for Galactic Cepheids

The projection factor (p), which converts the radial velocity to pulsational velocity, is an important parameter in the Baade-Wesselink (BW) type analysis and distance scale work. The p-factor is either adopted as a constant or linearly depending on the logarithmic of pulsating periods. The aim of this work is to calibrate the p-factor if a Cepheid has both the BW distance and an independent distance measurement, and examine the p-factor for delta Cephei -- the prototype of classical Cepheids. We calibrated the p-factor for several Galactic Cepheids that have both the latest BW distances and independent distances either from Hipparcos parallaxes or main-sequence fitting distances to Cepheid-hosted stellar clusters. Based on 25 Cepheids, the calibrated p-factor relation is consistent with latest p-factor relation in literature. The calibrated p-factor relation also indicates that this relation may not be linear and may exhibit an intrinsic scatter. We also examined the discrepancy of empirical p-factors for delta Cephei, and found that the reasons for this discrepancy include the disagreement of angular diameters, the treatment of radial velocity data, and the phase interval adopted during the fitting procedure. Finally, we investigated the impact of the input p-factor in two BW methodologies for delta Cephei, and found that different p-factors can be adopted in these BW methodologies and yet result in the same angular diameters.Comment: 6 pages, 6 figures and 2 tables. A&A accepte

The Shape and Scale of Galactic Rotation from Cepheid Kinematics

A catalog of Cepheid variables is used to probe the kinematics of the Galactic disk. Radial velocities are measured for eight distant Cepheids toward l = 300; these new Cepheids provide a particularly good constraint on the distance to the Galactic center, R_0. We model the disk with both an axisymmetric rotation curve and one with a weak elliptical component, and find evidence for an ellipticity of 0.043 +/- 0.016 near the Sun. Using these models, we derive R_0 = 7.66 +/- 0.32 kpc and v_circ = 237 +/- 12 km/s. The distance to the Galactic center agrees well with recent determinations from the distribution of RR Lyrae variables, and disfavors most models with large ellipticities at the solar orbit.Comment: 36 pages, LaTeX, 10 figure

Neighborhood and Social Environmental Influences on Child Chronic Disease Prevalence

We investigate how distinct residential environments uniquely influence chronic child disease. Aggregating over 200,000 pediatric geocoded medical records to the census tract of residence and linking them to neighborhood-level measures, we use multiple data analysis techniques to assess how heterogeneous exposures of social and environmental neighborhood conditions influence an index of child chronic disease (CCD) prevalence for the neighborhood. We find there is a graded relationship between degree of overall neighborhood disadvantage and children’s chronic disease such that the highest neighborhood CCD scores reside in communities with the highest concentrated disadvantage. Finally, results show that higher levels of neighborhood concentrated disadvantage and air pollution exposure associate with higher risks of having at least one chronic condition for children after also considering their individual- and family-level characteristics. Overall, our analysis serves as a comprehensive start for future researchers interested in assessing which neighborhood factors matter most for child chronic health conditions

Child Obesity and the Interaction of Family and Neighborhood Socioeconomic Context

The literature on neighborhoods and child obesity links contextual conditions to risk, assuming that if place matters, it matters in a similar way for everyone in those places. We explore the extent to which distinctive neighborhood types give rise to social patterning that produces variation in the odds of child obesity. We leverage geocoded electronic medical records for a diverse sample of over 135,000 children aged 2 to 12 and latent profile modeling to characterize places into distinctive neighborhood contexts. Multilevel models with cross-level interactions between neighborhood type and family socioeconomic standing (SES) reveal that children with different SES, but living in the same neighborhoods, have different odds of obesity. Specifically, we find lower-SES children benefit, but to a lesser degree, from neighborhood advantages and higher-SES children are negatively influenced, to a larger degree, by neighborhood disadvantages. The resulting narrowing of the gap in obesity by neighborhood disadvantage helps clarify how place matters for children’s odds of obesity and suggests that efforts to improve access to community advantages as well as efforts to address community disadvantages are important to curbing obesity and improving the health of all children

WhatsApp-propriate? A retrospective content analysis of WhatsApp use and potential breaches in confidentiality among a team of doctors at a district hospital, South Africa

Background. There has been a steady increase in the use of electronic media and instant messaging among healthcare professionals, where it has been almost universally adopted in the workplace. The use of WhatsApp and its perceived benefits in healthcare have been extensively studied; however, there are concerns regarding the potential for ethical breaches in confidentiality through shared electronic patient information.Objectives. To identify the usage characteristics and incidence of shared patient information with WhatsApp use in a team of medical doctors in an unobserved and unregulated setting.Methods. We conducted a retrospective cross-sectional content analysis of WhatsApp messages (n=3 340) among a team of 20 doctors in a South African district hospital over 6 months. All messages found within this time period were allocated unique identifiers. The text and image messages were thematically grouped into four categories, i.e. clinical care, resource allocation, social and administrative. Messages that contained patient-identifying information were included in the analysis.Results. Of a total of 3 340 messages sent, 220 (6.6%) contained patient-identifying information. Of these, 109 (3.3%) contained non-anonymised patient information, while in 111 (3.3%) messages, the information was anonymised. The likelihood of sharing patient identifiers was proportionally much higher in shared images (odds ratio (OR) 5.1; 95% confidence interval (CI) 3.2 - 8.2; p<0.0001) compared with text messages, and in messages that related to clinical care (OR 9.3; 95% CI 2.2 - 38.8; p=0.0023) compared with those sent for resource allocation, and social or administrative purposes.Conclusions. Non-anonymised patient identifiers were found in 3.3% of messages, constituting the potential for breaching patient confidentiality. While WhatsApp groups have significant utility in co-ordinating aspects of clinical care, resource allocation, as well as social and administrative functions, the safe use of WhatsApp should be promoted to ensure that patient confidentiality is maintained