Aberration and the Speed of Gravity

The observed absence of gravitational aberration requires that ``Newtonian'' gravity propagate at a speed $c_g>2\times10^{10}c$. By evaluating the gravitational effect of an accelerating mass, I show that aberration in general relativity is almost exactly canceled by velocity-dependent interactions, permitting $c_g=c$. This cancellation is dictated by conservation laws and the quadrupole nature of gravitational radiation.Comment: 9 pages, LaTeX, one figure using LaTeX picture environment; references added, abstract shortened, typos corrected, discussion of aberration and radiation reaction amplified; no change in essential argumen

Severe Coarctation of the Aorta: A Delayed Diagnosis

INTRODUCTION: Coarctation of the aorta (CoA) is a congenital heart disease characterized by narrowing of the aorta near the aortic isthmus. The incidence of CoA is 4 out of every 10,000 births, accounting for 6–8% of all congenital heart disease. It is common for CoA to be accompanied by other cardiovascular abnormalities, such as bicuspid aortic valve, ventricular septal defects, and mitral valve stenosis. Early diagnosis and treatment of CoA is crucial to improving morbidity and mortality associated with this disease as the mean age of death in untreated coarctation is 34 years. CASE DESCRIPTION: A 10 year old male presented to the outpatient pediatric clinic for an acute illness. On examination, he was found to be hypertensive with a blood pressure of 126/69 accompanied by a systolic heart murmur. Medical history included the diagnosis of a heart murmur at a 2 year well child examination before the patient was lost to follow-up until age 9. Upon re-establishment he was noted to have a II/VI systolic heart murmur. He was seen multiple times during year 10 of life where this murmur was consistently documented. Referral to cardiology for further evaluation was made. At presentation to the cardiologist, patient was found to be well appearing with clear lung sounds and a III/VI systolic murmur heard best at the left upper sternal boarder with radiation throughout the chest. During examination absent femoral and lower extremity pulses with pale lower extremity nail beds were also noted. Echocardiogram demonstrated severe CoA, bicuspid aortic valve, and aortic root dilatation. He was started on metoprolol for aortic root dilatation. Referral for heart catheterization was made for planned stenting to relieve the coarctation. DISCUSSION: Heart murmurs are a common finding on pediatric exams. The primary care provider typically determines which heart murmurs are pathologic and require follow-up. In the setting of a heart murmur there are clinical signs that indicate when further follow-up with cardiology is needed, including absent distal pulses, hypertension, radiation of the murmur throughout the chest, and discrepancy between upper and lower extremity blood pressure. Early referral to cardiology is imperative for any murmur that is not innocent to prevent delayed diagnosis of pathologic lesions. This case demonstrates the importance of checking blood pressure and lower extremity pulses in the setting of an asymptomatic patient with a heart murmur.N

Active Galactic Nuclei and the Truncation of Star Formation in K+A Galaxies

We have searched for active galactic nuclei (AGNs) in K+A galaxies, using multiwavelength imaging and spectroscopy in the Bootes field of the NOAO Deep Wide-Field Survey. The K+A galaxies, which have had their star formation rapidly truncated, are selected via their strong Balmer absorption lines and weak H-alpha emission. Our sample consists of 24 K+A galaxies selected from 6594 0.10<z<0.35 galaxies brighter than I=20 with optical spectroscopy from the AGN and Galaxy Evolution Survey. Two thirds of the K+A galaxies are likely ongoing galaxy mergers, with nearby companion galaxies or tidal tails. Galaxy mergers may be responsible for the truncation of star formation, or we are observing the aftermath of merger triggered starbursts. As expected, the optical colors of K+A galaxies largely fall between blue galaxies with ongoing star formation and red passive galaxies. However, only 1% of the galaxies with colors between the red and blue populations are K+A galaxies, and we conclude that the truncation of star formation in K+A galaxies must have been unusually abrupt (<100 Myr). We examined the AGN content of K+A galaxies with both optical emission-line ratios (BPT diagrams) and Chandra X-ray imaging. At least half of all K+A galaxies display the optical emission-line ratios of AGNs, and a third of M_R<-22 K+A galaxies host AGNs with X-ray luminosities of 10^{42} erg/s. The faintest K+A galaxies do not show clear evidence for hosting AGNs, having emission-line ratios consistent with photoionization by massive stars and few X-ray detections. We speculate that two mechanisms may be responsible for the truncation of star formation in K+A galaxies, with AGN feedback only playing a role in M_R<-20.5 galaxies.Comment: Accepted for publication in the Astrophysical Journal. 13 pages, 8 figure

High Crime Neighborhoods as a Driver for Toxic Stress Leading to Asthma

BACKGROUND: Social determinants of health and allostatic load theory suggest social environment can drive asthma diagnoses via the mechanism of toxic stress, the prolonged activation of stress response systems. While research has linked neighborhood crime to asthma, multivariate causal modeling has not been used to test toxic stress as the mechanism that links the two. The current study investigates neighborhood crime as a driver of pediatric asthma diagnoses via toxic stress. METHODS: A retrospective geospatial analysis of health and crime data was conducted. Health data was collected from the OU-Tulsa General Pediatric Clinic’s Electronic Medical Record while crime data was collected from the Tulsa Police Department. All variables were mapped geospatially using census tract as the unit of analysis. Structural equation modeling was used to test the causal model. Neighborhood crime indicators included homicide, rape, and narcotic-related offenses. Diagnoses of conduct, attention deficit, and other anxiety disorders were used in the analysis as toxic stress indicators. Asthma diagnoses were the outcome variable. To further test the model, data from 2016 was used as a calibration sample while data from 2017 was used as a validation sample. RESULTS: A full mediation model of high crime neighborhoods (n = 134) as a driver of toxic stress resulting in increased asthma diagnoses fit the 2016 data well (Χ2 = 15.6, p =.27; df = 13; RMSEA = .04 [90% CI: .00, .10]; CFI: .99; SRMR = .04). The results indicated the model accounted for 78% (R2 = .78) of the variance in asthma diagnoses. The model also provided a good fit to the 2017 data (X2= 23.6, p<.001; df= 13; RMSEA = .08 [90% CI: .02, .13]; CFI: .96; SRMR=.06). CONCLUSION: The results of the current study have important practice and research implications. While clinicians and researchers have become increasingly aware of the impact of social determinants of health, there has been little focus on improving clinical practices. Physicians interested in alleviated the burden of toxic stress and asthma should explore ways to reduce neighborhood crime at the policy level while also being aware of each of their patients’ unique circumstances in relation to where they live.N

Young ages and other intriguing properties of massive compact galaxies in the Local Universe

We characterize the kinematics, morphology, stellar populations and star formation histories of a sample of massive compact galaxies in the nearby Universe, which might provide a closer look to the nature of their high redshift (z > 1.0) massive counterparts. We find that nearby compact massive objects show elongated morphologies and are fast rotators. New high-quality long-slit spectra show that they have young mean luminosity-weighted ages (< 2Gyr) and solar metallicities or above ([Z/H]> 0.0). No significant stellar population gradients are found. The analysis of their star formation histories suggests that these objects have experienced recently enormous bursts which, in some cases, represent unprecedented large fractions of their total stellar mass. These galaxies seem to be truly unique, as they do not follow the characteristic kinematical and stellar population patterns of present-day massive ellipticals, spirals or even dwarfs.Comment: 16 pages, 11 figures; Accepted for publication in MNRA