An improved method for estimating source densities using the temporal distribution of Cosmological Transients

It has been shown that the observed temporal distribution of transient events in the cosmos can be used to constrain their rate density. Here we show that the peak flux--observation time relation takes the form of a power law that is invariant to the luminosity distribution of the sources, and that the method can be greatly improved by invoking time reversal invariance and the temporal cosmological principle. We demonstrate how the method can be used to constrain distributions of transient events, by applying it to Swift gamma-ray burst data and show that the peak flux--observation time relation is in good agreement with recent estimates of source parameters. We additionally show that the intrinsic time dependence allows the method to be used as a predictive tool. Within the next year of Swift observation, we find a 50% chance of obtaining a peak flux greater than that of GRB 060017 -- the highest Swift peak flux to date -- and the same probability of detecting a burst with peak flux > 100 photons s^{-1} cm^{-2} within 6 years.Comment: Submitted to ApJ Letter

An Exploration of Racial/Ethnic Differences in the Association between Perfectionism and Disordered Eating in College Students

Perfectionism is a robust risk factor for eating disorders (EDs). Although individually-oriented dimensions of perfectionism are strongly related to eating pathology, less is known about the contribution of parent-oriented dimensions, specifically parental expectations (PE) and parental criticisms (PC). Further, few studies have investigated these effects within racially/ethnically diverse samples. However, PE and PC might be particularly relevant to eating pathology among certain cultural groups, such as those from collectivistic and interdependent societies. This study examined associations among PE, PC, and ED symptoms across racial/ethnic groups. Undergraduates (N=706; 74.8% Female; 48% White, 19.8% Black, 7.1% Latinx, 16% Asian, 9.1% multiracial) completed online surveys assessing perfectionism and ED symptoms. Multiple and logistic regressions examined the association between parent-oriented perfectionism, global eating pathology, loss-of-control (LOC) eating, purging behaviors, and ED risk status (EDE-Q global \u3c 4.0). Analyses were conducted by racial/ethnic group, controlling for gender. Both PE and PC were related to greater ED pathology in students identifying as White (pp=.03), Asian (p=.02), and multiracial (pp=.19). Higher PC was related to a greater likelihood of endorsing LOC eating in White (p=.004) and Black students (p=.05) and purging behaviors in White (p=.004), Asian (p=.04), and multiracial students (p=.03). Greater PC was also associated with ED risk in Asian (p=.03) and multiracial participants (p=.01). Findings indicate that the relations between specific aspects of parent-oriented perfectionism differ among cultural groups and are associated with ED symptoms in college students. PC seemed more relevant to ED pathology than did PE overall. Findings suggest that parent-oriented perfectionism, particularly PC, might be important to include in clinical assessment and treatment with students at-risk of EDs.https://scholarscompass.vcu.edu/gradposters/1039/thumbnail.jp

Using temporal distributions of transient events to characterize cosmological source populations

The brightest events in a time series of cosmological transients obey an observation time dependence which is often overlooked. This dependence can be exploited to probe the global properties of electromagnetic and gravitational wave transients (Howell et al. 2007a, Coward & Burman 2005). We describe a new relation based on a peak flux--observation time distribution and show that it is invariant to the luminosity distribution of the sources (Howell et al. 2007b). Applying this relation, in combination with a new data analysis filter, to \emph{Swift} gamma-ray burst data, we demonstrate that it can constrain their rate density.Comment: published in proceedings of FRONTIERS OF FUNDAMENTAL AND COMPUTATIONAL PHYSICS: 10th International Symposium, AIP,1246,203, (2010

Fabrication of titanium multi-wall Thermal Protection System (TPS) test panel arrays

Several arrays were designed and tested. Tests included vibrational and acoustical tests, radiant heating tests, and thermal conductivity tests. A feasible manufacturing technique was established for producing the protection system panels

Re-design and fabrication of titanium multi-wall Thermal Protection System (TPS) test panels

The Titanium Multi-wall Thermal Protection System (TIPS) panel was re-designed to incorporate Ti-6-2-4-2 outer sheets for the hot surface, ninety degree side closures for ease of construction and through panel fastness for ease of panel removal. Thermal and structural tests were performed to verify the design. Twenty-five panels were fabricated and delivered to NASA for evaluation at Langley Research Center and Johnson Space Center

A holistic approach to fieldwork through balanced reflective practice

Reflective practice is well-established as a tool for practitioner development in areas such as nursing, social work and education. Reflection involves the integration of theoretical constructs and practical action; therefore it seems somewhat ironic that there is little written on reflective practice within the natural sciences – where theory and action are often juxtaposed. This paper attempts to address this gap through examining biological fieldwork in relation to a balanced system of reflection that embraces the cognitive, psychomotor, affective and conative aspects of practice. A model of reflective practice that asks practitioners to log their reflections against these four domains was applied to a biodiversity survey of tropical mountain streams in Trinidad. It was found that there is clear evidence that biological fieldwork can embrace a reflective methodology and that reflective practice can be used in fieldwork as a tool for making explicit that which is already implicit. A holistic vision of fieldwork is sketched out here, where the introduction of a balanced model of reflective practice can support an approach that moves beyond the consideration of the environment and the researcher as two separate entities and, instead, considers the relationship between environment and researcher.PostprintPeer reviewe

SUSY-Breaking Parameters from RG Invariants at the LHC

We study Renormalization Group invariant (RGI) quantities in the Minimal Supersymmetric Standard Model and show that they are a powerful and simple instrument for testing high scale models of supersymmetry (SUSY)-breaking. For illustration, we analyze the frameworks of minimal and general gauge mediated (MGM and GGM) SUSY-breaking, with additional arbitrary soft Higgs mass parameters at the messenger scale. We show that if a gaugino and two first generation sfermion soft masses are determined at the LHC, the RGIs lead to MGM sum rules that yield accurate predictions for the other gaugino and first generation soft masses. RGIs can also be used to reconstruct the fundamental MGM parameters (including the messenger scale), calculate the hypercharge D-term, and find relationships among the third generation and Higgs soft masses. We then study the extent to which measurements of the full first generation spectrum at the LHC may distinguish different SUSY-breaking scenarios. In the case of MGM, although most deviations violate the sum rules by more than estimated experimental errors, we find a 1-parameter family of GGM models that satisfy the constraints and produce the same first generation spectrum. The GGM-MGM degeneracy is lifted by differences in the third generation masses and the messenger scales.Comment: (v1) 30 pages; (v2) mislabeling in figs 2 and 3 corrected, version accepted for publication in Phys. Rev.

On the gravitational wave background from compact binary coalescences in the band of ground-based interferometers

This paper reports a comprehensive study on the gravitational wave (GW) background from compact binary coalescences. We consider in our calculations newly available observation-based neutron star and black hole mass distributions and complete analytical waveforms that include post-Newtonian amplitude corrections. Our results show that: (i) post-Newtonian effects cause a small reduction in the GW background signal; (ii) below 100 Hz the background depends primarily on the local coalescence rate $r_0$ and the average chirp mass and is independent of the chirp mass distribution; (iii) the effects of cosmic star formation rates and delay times between the formation and merger of binaries are linear below 100 Hz and can be represented by a single parameter within a factor of ~ 2; (iv) a simple power law model of the energy density parameter $\Omega_{GW}(f) ~ f^{2/3}$ up to 50-100 Hz is sufficient to be used as a search template for ground-based interferometers. In terms of the detection prospects of the background signal, we show that: (i) detection (a signal-to-noise ratio of 3) within one year of observation by the Advanced LIGO detectors (H1-L1) requires a coalescence rate of $r_0 = 3 (0.2) Mpc^{-3} Myr^{-1}$ for binary neutron stars (binary black holes); (ii) this limit on $r_0$ could be reduced 3-fold for two co-located detectors, whereas the currently proposed worldwide network of advanced instruments gives only ~ 30% improvement in detectability; (iii) the improved sensitivity of the planned Einstein Telescope allows not only confident detection of the background but also the high frequency components of the spectrum to be measured. Finally we show that sub-threshold binary neutron star merger events produce a strong foreground, which could be an issue for future terrestrial stochastic searches of primordial GWs.Comment: A few typos corrected to match the published version in MNRA