Reba Cooper, Laverne McLaughlin, and Dian Ray in a Joint Junior Recital

This is the program for the joint junior recital of pianist Reba Cooper, organist Laverne McLaughlin, and pianist Dian Ray. The recital took place on March 28, 1963, in Mitchell Hall Auditorium

X-Ray Observations of Black Widow Pulsars

We describe the first X-ray observations of five short orbital period ($P_B < 1$ day), $\gamma$-ray emitting, binary millisecond pulsars. Four of these, PSRs J0023+0923, J1124$-$3653, J1810+1744, and J2256$-$1024 are `black-widow' pulsars, with degenerate companions of mass $\ll0.1 M_{\odot}$, three of which exhibit radio eclipses. The fifth source, PSR J2215+5135, is an eclipsing `redback' with a near Roche-lobe filling $\sim$0.2 solar mass non-degenerate companion. Data were taken using the \textit{Chandra X-Ray Observatory} and covered a full binary orbit for each pulsar. Two pulsars, PSRs J2215+5135 and J2256$-$1024, show significant orbital variability while PSR J1124$-$3653 shows marginal orbital variability. The lightcurves for these three pulsars have X-ray flux minima coinciding with the phases of the radio eclipses. This phenomenon is consistent with an intrabinary shock emission interpretation for the X-rays. The other two pulsars, PSRs J0023+0923 and J1810+1744, are fainter and do not demonstrate variability at a level we can detect in these data. All five spectra are fit with three separate models: a power-law model, a blackbody model, and a combined model with both power-law and blackbody components. The preferred spectral fits yield power-law indices that range from 1.3 to 3.2 and blackbody temperatures in the hundreds of eV. The spectrum for PSR J2215+5135 shows a significant hard X-ray component, with a large number of counts above 2 keV, which is additional evidence for the presence of intrabinary shock emission and is similar to what has been detected in the low-mass X-ray binary to millisecond pulsar transition object PSR J1023+0038.Comment: 8 pages, 6 figures, 2 tables, submitted to Ap

Arecibo timing and single-pulse observations of 17 pulsars

We report on timing and single-pulse observations of 17 pulsars discovered at the Arecibo observatory. The highlights of our sample are the recycled pulsars J1829+2456, J1944+0907 and the drifting subpulses observed in PSR J0815+0939. For the double neutron star binary J1829+2456, in addition to improving upon our existing measurement of relativistic periastron advance, we have now measured the pulsar's spin period derivative. This new result sets an upper limit on the transverse speed of 120 km/s and a lower limit on the characteristic age of 12.4 Gyr. From our measurement of proper motion of the isolated 5.2-ms pulsar J1944+0907, we infer a transverse speed of 188 +/- 65 km/s. This is higher than that of any other isolated millisecond pulsar. An estimate of the speed, using interstellar scintillation, of 235 +/- 45 km/s indicates that the scattering medium along the line of sight is non-uniform. We discuss the drifting subpulses detected from three pulsars in the sample, in particular the remarkable drifting subpulse properties of the 645-ms pulsar J0815+0939. Drifting is observed in all four components of the pulse profile, with the sense of drift varying among the different components. This unusual `bi-drifting'' behaviour challenges standard explanations of the drifting subpulse phenomenon.Comment: 9 pages, 6 figures. Accepted for publication in MNRA

Polyacrylate grafted graphene oxide nanocomposites for biomedical applications

[[abstract]]Utilizing a reverse micelle process, we have grafted polyacrylate (P) on graphene oxide (GO) to realize polyacrylate grafted graphene oxide (P-GO) nanocomposites, upon whose subsequent reduction, polyacrylate grafted reduced graphene oxide (P-rGO) nanocomposites are achieved. Using techniques such as ultraviolet photoelectron spectroscopy (UPS), x-ray photoelectron spectroscopy, and x-ray absorption near edge structure (XANES) spectroscopy, in conjunction with high-resolution microscopy, Raman spectroscopy, and superconducting quantum interference device analysis, we have studied in depth the electronic, microstructural, electrical, and magnetic properties of these P-GO and P-rGO nanocomposites. While polyacrylate grafting ensures a high solubility of P-GO and P-rGO, the P-rGO nanocomposites additionally show a near doubling of the paramagnetic response (9.6 × 10−3 emu/g) as compared to the r-GO (5.6 × 10−3 emu/g) and P-GO (5.5 × 10−3 emu/g), respectively, at 2 K. The grafting of diamagnetic polyacrylate enhances the magnetic response for the P-GO and P-rGO owing to the increase in the defect states, sp3-type bonding, and enhanced magnetic coupling between the magnetic moments arising due to the presence of nitrogen functionalities. This behavior is further corroborated via the measurements of the electronic structure by XANES and UPS measurements. Thus, the possibility of manipulation of the magnetic behavior along with the abundance of surface functional groups makes both P-GO and P-rGO nanocomposites highly conducive for deriving water-soluble functionalized graphene by linking affinity molecules with polyacrylate backbone for biological and biomedical applications.[[notice]]補正完

A Reevaluation of the Effects of State and Federal Dependent Coverage Mandates on Health Insurance Coverage

State governments have been passing laws mandating insurers to allow young adults to stay on their parents' health insurance plans past the age of 19 since the 1970s. These laws were intended to increase coverage, but research has been inconclusive on whether they were successful. We reconsider the issue with an improved approach featuring three key elements: a new, accurate dataset on state mandates; recognition that effects could differ greatly by age due to take up rate differences; and avoidance of endogenous characteristics when identifying mandate eligible young adults. We find the impact of the state mandates was concentrated among the 19 to 22 age group, for which dependent coverage increased sharply by about 6 percentage points. Overall coverage increased by almost 3 percentage points, with the difference explained by crowd out of public insurance. Crowd out of coverage through young adults own jobs was negligible. For those above age 22, we find little evidence of changes in coverage. We incorporate these insights into analysis of the Affordable Care Act (ACA) dependent coverage mandate, showing its effects were focused among those whom were previously ineligible for state mandates, or were eligible but older than 22. We argue the ACA's impact was broader because it had fewer eligibility conditions that implied parental dependence; young adults could be on their parents' insurance but still be relatively independent

Discovery of the Optical Counterparts to Four Energetic Fermi Millisecond Pulsars

In the last few years, over 43 millisecond radio pulsars have been discovered by targeted searches of unidentified gamma-ray sources found by the Fermi Gamma-Ray Space Telescope. A large fraction of these millisecond pulsars are in compact binaries with low-mass companions. These systems often show eclipses of the pulsar signal and are commonly known as black widows and redbacks because the pulsar is gradually destroying its companion. In this paper, we report on the optical discovery of four strongly irradiated millisecond pulsar companions. All four sources show modulations of their color and luminosity at the known orbital periods from radio timing. Light curve modelling of our exploratory data shows that the equilibrium temperature reached on the companion's dayside with respect to their nightside is consistent with about 10-30% of the available spin-down energy from the pulsar being reprocessed to increase the companion's dayside temperature. This value compares well with the range observed in other irradiated pulsar binaries and offers insights about the energetics of the pulsar wind and the production of gamma-ray emission. In addition, this provides a simple way of estimating the brightness of irradiated pulsar companions given the pulsar spin-down luminosity. Our analysis also suggests that two of the four new irradiated pulsar companions are only partially filling their Roche lobe. Some of these sources are relatively bright and represent good targets for spectroscopic follow-up. These measurements could enable, among other things, mass determination of the neutron stars in these systems.Comment: 11 pages, 5 tables, 1 figure, 4 online tables. ApJ submitted and referee