The ‘Homework Gap’ and Academic Achievement in High School Science: An Ecological Perspective for Policymakers and Practitioners

Information and communication technologies (ICTs) are increasingly required within K-12 educational settings, yet the impact of youth’s access to and use of digital resources outside of the classroom on academic achievement is only beginning to be explored in the literature. This study used data from the Fragile Families & Child Wellbeing Study to assess the relationship between grades in high school science and digital equity across the learner’s ecological environment. Digital inequities experienced by school-aged youth are referred to as the homework gap. The COVID-19 pandemic placed new urgency on resolving the homework gap as millions of students shifted to full-time online or learning at home during the pandemic. Study findings show that ICT access and use across ecological domains is a significant predictor of urban youths’ academic achievement in science

Where are the shareholders’ mansions? CEOs’ home purchases, stock sales, and subsequent company performance

We study real estate purchases by major company CEOs, compiling a database of the principal residences of nearly every top executive in the Standard & Poor’s 500 index. When a CEO buys real estate, future company performance is inversely related to the CEO’s liquidation of company shares and options for financing the transaction. We also find that, regardless of the source of finance, future company performance deteriorates when CEOs acquire extremely large or costly mansions and estates. We therefore interpret large home acquisitions as signals of CEO entrenchment. Our research also provides useful insights for calibrating utility based models of executive compensation and for understanding patterns of Veblenian conspicuous consumption

Magnetic substructure in the northern Fermi Bubble revealed by polarized WMAP emission

We report a correspondence between giant, polarized microwave structures emerging north from the Galactic plane near the Galactic center and a number of GeV gamma-ray features, including the eastern edge of the recently-discovered northern Fermi Bubble. The polarized microwave features also correspond to structures seen in the all-sky 408 MHz total intensity data, including the Galactic center spur. The magnetic field structure revealed by the polarization data at 23 GHz suggests that neither the emission coincident with the Bubble edge nor the Galactic center spur are likely to be features of the local ISM. On the basis of the observed morphological correspondences, similar inferred spectra, and the similar energetics of all sources, we suggest a direct connection between the Galactic center spur and the northern Fermi Bubble.Comment: Accepted for publication in The Astrophysical Journal Letters after minor change

Strong Evidence that the Galactic Bulge is Shining in Gamma Rays

There is growing evidence that the Galactic Center Excess identified in the $\textit{Fermi}$-LAT gamma-ray data arises from a population of faint astrophysical sources. We provide compelling supporting evidence by showing that the morphology of the excess traces the stellar over-density of the Galactic bulge. By adopting a template of the bulge stars obtained from a triaxial 3D fit to the diffuse near-infrared emission, we show that it is detected at high significance. The significance deteriorates when either the position or the orientation of the template is artificially shifted, supporting the correlation of the gamma-ray data with the Galactic bulge. In deriving these results, we have used more sophisticated templates at low-latitudes for the $\textit{Fermi}$ bubbles compared to previous work and the three-dimensional Inverse Compton (IC) maps recently released by the ${\tt GALPROP}$ team. Our results provide strong constraints on Millisecond Pulsar (MSP) formation scenarios proposed to explain the excess. We find that an $\textit{admixture formation}$ scenario, in which some of the relevant binaries are $\textit{primordial}$ and the rest are formed $\textit{dynamically}$, is preferred over a primordial-only formation scenario at $7.6\sigma$ confidence level. Our detailed morphological analysis also disfavors models of the disrupted globular clusters scenario that predict a spherically symmetric distribution of MSPs in the Galactic bulge. For the first time, we report evidence of a high energy tail in the nuclear bulge spectrum that could be the result of IC emission from electrons and positrons injected by a population of MSPs and star formation activity from the same site.Comment: 21 pages, 13 figures, V2: Minor changes to match submitted version, V3: matches JCAP published versio

Radio Synchrotron Emission from Secondary Leptons in the Vicinity of Sgr A*

A point-like source of ~TeV gamma-rays has recently been seen towards the Galactic center by HESS and other air Cerenkov telescopes. In recent work (Ballantyne et al. 2007), we demonstrated that these gamma-rays can be attributed to high-energy protons that (i) are accelerated close to the event horizon of the central black hole, Sgr A*, (ii) diffuse out to ~pc scales, and (iii) finally interact to produce gamma-rays. The same hadronic collision processes will necessarily lead to the creation of electrons and positrons. Here we calculate the synchrotron emissivity of these secondary leptons in the same magnetic field configuration through which the initiating protons have been propagated in our model. We compare this emission with the observed ~GHz radio spectrum of the inner few pc region which we have assembled from archival data and new measurements we have made with the Australia Telescope Compact Array. We find that our model predicts secondary synchrotron emission with a steep slope consistent with the observations but with an overall normalization that is too large by a factor of ~ 2. If we further constrain our theoretical gamma-ray curve to obey the implicit EGRET upper limit on emission from this region we predict radio emission that is consistent with observations, i.e., the hadronic model of gamma ray emission can, simultaneously and without fine-tuning, also explain essentially all the diffuse radio emission detected from the inner few pc of the Galaxy.Comment: 11 pages, 2 figures. Two references missing from published version added and acknowledgements extende

Where Are the Shareholders’ Mansions? CEOs’ Home Purchases, Stock Sales, and Subsequent Company Performance

We study real estate purchases by major company CEOs, compiling a database of the principal residences of nearly every top executive in the Standard & Poor’s 500 index. When a CEO buys real estate, future company performance is inversely related to the CEO’s liquidation of company shares and options for financing the transaction. We also find that, regardless of the source of finance, future company performance deteriorates when CEOs acquire extremely large or costly mansions and estates. We therefore interpret large home acquisitions as signals of CEO entrenchment. Our research also provides useful insights for calibrating utility based models of executive compensation and for understanding patterns of Veblenian conspicuous consumption

Wild at Heart:-The Particle Astrophysics of the Galactic Centre

We treat of the high-energy astrophysics of the inner ~200 pc of the Galaxy. Our modelling of this region shows that the supernovae exploding here every few thousand years inject enough power to i) sustain the steady-state, in situ population of cosmic rays (CRs) required to generate the region's non-thermal radio and TeV {\gamma}-ray emis-sion; ii) drive a powerful wind that advects non-thermal particles out of the inner GC; iii) supply the low-energy CRs whose Coulombic collisions sustain the temperature and ionization rate of the anomalously warm, envelope H2 detected throughout the Cen-tral Molecular Zone; iv) accelerate the primary electrons which provide the extended, non-thermal radio emission seen over ~150 pc scales above and below the plane (the Galactic centre lobe); and v) accelerate the primary protons and heavier ions which, advected to very large scales (up to ~10 kpc), generate the recently-identified WMAP haze and corresponding Fermi haze/bubbles. Our modelling bounds the average magnetic field amplitude in the inner few degrees of the Galaxy to the range 60 < B/microG < 400 (at 2 sigma confidence) and shows that even TeV CRs likely do not have time to penetrate into the cores of the region's dense molecular clouds before the wind removes them from the region. This latter finding apparently disfavours scenarios in which CRs - in this star-burst-like environment - act to substantially modify the conditions of star-formation. We speculate that the wind we identify plays a crucial role in advecting low-energy positrons from the Galactic nucleus into the bulge, thereby explaining the extended morphology of the 511 keV line emission. (abridged)Comment: One figure corrected. Accepted for publication in MNRAS. 29 pages, 14 figure

Application of Carbon Dioxide Waveguide Lasers to Infrared Saturation Spectroscopy

The development of tunable lasers has made possible spectroscopy at a resolution previously unattainable. Although continuous-wave broadly tunable sources in the 10 pm region do not yet exist , waveguide carbon dioxide lase r s offer a useful tunability about a large number of emission lines in this part of the spectrum. The first part of this thesis contains a review ·or waveguide Co2 laser theory and previous wo r k on these devices. A design intended for high resolution spectroscopy is then described. Two of these lasers have been used in a spectrometer , using a saturated fluorescence to provide a stable and calibrated reference and a microprocessor- based system for control and monitoring of the tunable source. The general principles are resolution limits of sub- Doppler saturation spectroscopy are also covered. The second part is a compendium of measurements taken and insights gained using the completed spectrometer. Collisional transitions between the hype fine components of a methyl iodide absorption have been observed . Precise measurements of phosphine absorption frequencies indicate that far - infrared lase r s may be pumped much further from resonance than has been assumed hitherto. Measurements on the allene molecule have provide:: improved constants for the v g= 1 state; the split ting of states by K- or 1- doubling has also been observed, confirming theoretical predictions. Finally, a· postulated Coriolis interaction between two modes of formic acid has been verified and quantified, and improved constants obtained for, both modes in a study bringing together measurements taken using the waveguide laser spectrometer and the microwave and submillimetre measurements of others