The radio continuum emission of star forming galaxies at low to high redshift

In this thesis, the radio-continuum emission of starburst galaxies is explored to understand the physical processes that trace star formation. Separating and constraining these processes require a broad, densely sampled spectral energy distribution that can be used to apply and constrain various radiative transfer models. Existing tracers of star formation include a suite of multi-wavelength diagnostics, including UV, optical, infrared, nebular transitions, and radio continuum. At present, optical and near infrared observations have been the most successful at probing the high redshift volume and constraining the star formation at the earliest epochs of the Universe. However, such approaches are critically awed in that they are subject to the effects of dust obscuration, requiring sophisticated methods to recover the intrinsic luminosities of the optical tracers of star formation. In the high redshift Universe, these corrections are increasingly compromised and uncertain. Radio-continuum measurements of star formation have the potential to be the most reliable in this high redshift regime because they are not affected by the presence of dust, allowing observers to acquire uncompromised measures of star formation. At frequencies below _ 2 GHz, the radio continuum is made up overwhelmingly by non-thermal synchrotron emission, produced by near light speed cosmic rays interacting with the large-scale magnetic structure of a galaxy. Although this type of emission is not a direct product of stars, it has been reasonably well calibrated to exploit the far-infrared to radio correlation to obtain a measure of star formation. Our current understanding of the far-infrared to radio correlation suggests that there should be an evolution as a function of redshifts; however, observationally evidence both confirms and rejects this evolution hypothesis. As the far-infrared to radio correlation is the foundation of star formation rate indicators based on the radio continuum for frequencies where synchrotron emission is a significant component of the observed spectrum, there is a requirement to investigate, and if necessary repair, radio-based star formation rate measures in preparation for radio telescopes like the Square Kilometre Array. Throughout my candidature, I have studied the spectral energy distribution of 30 local galaxies that were selected based on their high star formation rates, as indicated by their radio and infrared emission data collected from existing surveys. Across a broad frequency range spanning 80MHz to 50 GHz, the underlying physical processes driving the radio continuum have been disentangled. By comparing these products to other multi-wavelength indicators of star formation, we can begin to understand the radio-based tracers for faint star forming galaxies at high redshift that the next generation of radio telescopes will reveal

The impact of a mentoring/financial incentive program on at-risk high school students

This mixed methods study describes some outcomes of Champions of Wayne, a privately funded mentoring/incentive program at an impoverished high school near Detroit. Over 500 students enroll in the program annually. The program involves providing high school students who choose to participate both adult mentoring and a $200 incentive to improve one\u27s grades each semester. The quantitative component of this study analyzes GPA data, while a multiple case study of six participants explores mentoring relationships and experiences. In a comparison of the GPA of participants versus non-participants, program participants significantly improve their grades when compared to those student who do not participate in the program. The study revealed that though students initially enroll because of the$200 incentive, they describe the achievement and mentoring to be most influential in the end. A trusting relationship with an educationally successful adult has potential to make a particularly positive impact on an at-risk student from a family with little (or no) educational tradition. The study concludes with recommendations for school leaders interested in implementing a similar program, as well as a speculative discussion of how the program may have a ripple effect on other teacher-student relationships and the overall culture of the school

A Cone Beam CT-Based Study For Clinical Target Definition Using Pelvic Anatomy During Post-Prostatectomy Radiotherapy

Introduction: Radiation therapy (RT) is delivered after radical prostatectomy (RP) either as salvage treatment for an elevated prostate-specific antigen (PSA) level1-6 or as adjuvant therapy for patients with highrisk pathologic features7-8. Recent prospective data demonstrated a disease-free survival benefit of adjuvant RT for pathologic T3N0 prostate cancer9-10. Despite literature supporting the delivery of post-RP RT to the prostatic fossa (PF), no clear target definition guidelines exist for intensity modulated radiation therapy (IMRT) or image-guided RT (IGRT)11. Visualization of the PF is limited on standard CT images, with significant interobserver variability and uncertainty in CTV definition12. Efforts to incorporate complementary imaging modalities such as MRI for PF target volume definition have generated neither demonstrably more reliable PF delineation, nor practical contouring guidelines13. Regardless of the imaging modality, direct visualization and delineation of the PF clinical target volume (CTV) is fraught with uncertainty. On the other hand, it is possible to distinguish the borders of important nearby pelvic structures, namely the bladder and the rectum. The reliability of rectal volume definition on helical CT is supported by analysis of rectal contours defined in a prospective trial, suggesting the feasibility of rectal dose-volume data collection in a multicenter setting14. Fiorino et al have described a correlation between PF CTV shift and anterior rectal wall shift for the cranial half of the rectum in their report of rectal and bladder movement during post-RP RT using weekly CT images15. These studies support the reliability of CT-defined rectum contours and a limited correlation between PF CTV and anterior rectal wall, an important tenet in the current study. Int. J. Radiation Oncol. Biol. Physics, Volume 70, Issue 2, pages 431-436, Feb. 1, 2008

Effect of reducing daily herbage allowance during early lactation on composition and processing characteristics of milk from spring-calved herds

peer-reviewedThe study investigated the effects of reducing daily herbage allowance (DHA) from 15.0 to 11.8 kg dry matter per cow (>3.5 cm post grazing sward height) to a spring-calved herd during early lactation on the composition, rennet coagulability and heat stability characteristics of milk during early lactation (EL, 29–70 days in milk, DIM), mid lactation (ML, 78–183 DIM), and late lactation (LL, 205–267 DIM). Samples of milk were taken at approximate 10 d intervals during EL and at 1–3 week intervals during ML and LL. Reducing DHA led to reductions in milk yield, milk solids yield, and concentrations of protein (∼0.22%, w/w) and casein (0.13%, w/w) during EL. Otherwise, it had little effect on milk composition or on the selected processing characteristics in ML, LL or overall lactation. Stage of lactation resulted in comparatively large changes in most compositional parameters, rennet gelation and heat stability

Grazing of dairy cows on pasture versus indoor feeding on total mixed ration: Effects on low-moisture part-skim Mozzarella cheese yield and quality characteristics in mid and late lactation

peer-reviewedThis study investigated the effects of 3 dairy cow feeding systems on the composition, yield, and biochemical and physical properties of low-moisture part-skim Mozzarella cheese in mid (ML; May–June) and late (LL; October–November) lactation. Sixty spring-calving cows were assigned to 3 herds, each consisting of 20 cows, and balanced on parity, calving date, and pre-experimental milk yield and milk solids yield. Each herd was allocated to 1 of the following feeding systems: grazing on perennial ryegrass (Lolium perenne L.) pasture (GRO), grazing on perennial ryegrass and white clover (Trifolium repens L.) pasture (GRC), or housed indoors and offered total mixed ration (TMR). Mozzarella cheese was manufactured on 3 separate occasions in ML and 4 in LL in 2016. Feeding system had significant effects on milk composition, cheese yield, the elemental composition of cheese, cheese color (green to red and blue to yellow color coordinates), the extent of flow on heating, and the fluidity of the melted cheese. Compared with TMR milk, GRO and GRC milks had higher concentrations of protein and casein and lower concentrations of I, Cu, and Se, higher cheese-yielding capacity, and produced cheese with lower concentrations of the trace elements I, Cu, and Se and higher yellowness value. Cheese from GRO milk had higher heat-induced flow and fluidity than cheese from TMR milk. These effects were observed over the entire lactation period (ML + LL), but varied somewhat in ML and LL. Feeding system had little, or no, effect on gross composition of the cheese, the proportions of milk protein or fat lost to cheese whey, the texture of the unheated cheese, or the energy required to extend the molten cheese. The differences in color and melt characteristics of cheeses obtained from milks with the different feeding systems may provide a basis for creating points of differentiation suited to different markets.This study was funded by the Department of Agriculture, Food and the Marine (Dublin, Ireland) Stimulus fund (11/sf/309), and additionally supported by funding from the Dairy Levy Trust Co-Operative Society Limited (Dublin, Ireland)

Low frequency radio continuum imaging and SED modeling of 11 LIRGs: radio-only and FUV to radio bands

We present the detailed analysis of 11 local luminous infrared galaxies (LIRGs) from ultraviolet through far-infrared to radio ($\sim$70 MHz to $\sim$15 GHz) bands. We derive the astrophysical properties through spectral energy distribution (SED) modeling using the Code Investigating GALaxy Emission (CIGALE) and UltraNest codes. The radio SEDs include our new observations at 325 and 610 MHz from the GMRT and the measurements from public archives. Our main results are (1) radio SEDs show turnovers and bends, (2) the synchrotron spectral index of the fitted radio spectra ranges between $-$0.5 and $-$1.7, and (3) the infrared luminosity, dust mass, dust temperature, stellar mass, star-formation rates (SFRs) and AGN fraction obtained from CIGALE falls in the range exhibited by galaxies of the same class. The ratio of 60$\mu$m infrared and 1.4 GHz radio luminosity, the 1.4 GHz thermal fraction, and emission measure range between 2.1 and 2.9, 0.1% and 10%, 0.02 and 269.5$\times$10$^{6}$ cm$^{-6}$ pc, respectively. We conclude that the turnovers seen in the radio SEDs are due to free-free absorption; this is supported by the low AGN fraction derived from the CIGALE analysis. The decomposed 1.4 GHz thermal and nonthermal radio luminosities allowed us to compute the star formation rate (SFR) using scaling relations. A positive correlation is observed between the SFR$_{IR}$ obtained 10 Myr ago (compared to 100 Myr ago) and 1.4 GHz radio (total and nonthermal) because similar synchrotron lifetimes are expected for typical magnetic field strengths observed in these galaxies ($\approx$50$\mu$G).Comment: ApJ accepted. Comments are welcom

Low-frequency radio continuum imaging and SED modeling of 11 LIRGs : radio-only and FUV to radio bands

We present a detailed analysis of 11 local luminous infrared galaxies from ultraviolet through far-infrared to radio (∼70 MHz to ∼15 GHz) bands. We derive the astrophysical properties through spectral energy distribution (SED) modeling using the Code Investigating GALaxy Emission (CIGALE) and UltraNest codes. The radio SEDs include our new observations at 325 and 610 MHz from the GMRT and the measurements from public archives. Our main results are (1) radio SEDs show turnovers and bends, (2) the synchrotron spectral index of the fitted radio spectra ranges between −0.5 and −1.7, and (3) the infrared luminosity, dust mass, dust temperature, stellar mass, star formation rates (SFRs), and active galactic nuclei (AGN) fraction obtained from CIGALE fall within the range exhibited by galaxies of the same class. The ratio of 60 μm infrared and 1.4 GHz radio luminosity, the 1.4 GHz thermal fraction, and emission measure range between 2.1 and 2.9, 0.1% and 10%, 0.02 and 269.5 $\times$ 10$^{6}$ cm$^{-6}$ pc, respectively. We conclude that the turnovers seen in the radio SEDs are due to free–free absorption; this is supported by the low AGN fraction derived from the CIGALE analysis. The decomposed 1.4 GHz thermal and nonthermal radio luminosities allowed us to compute the SFR using scaling relations. A positive correlation is observed between the SFR$_{IR}$ obtained 10 Myr ago (compared to 100 Myr ago) and 1.4 GHz radio (total and nonthermal) because similar synchrotron lifetimes are expected for typical magnetic field strengths observed in these galaxies (≈50 μG)