The Overlooked Potential of Generalized Linear Models in Astronomy - I: Binomial Regression

Revealing hidden patterns in astronomical data is often the path to fundamental scientific breakthroughs; meanwhile the complexity of scientific inquiry increases as more subtle relationships are sought. Contemporary data analysis problems often elude the capabilities of classical statistical techniques, suggesting the use of cutting edge statistical methods. In this light, astronomers have overlooked a whole family of statistical techniques for exploratory data analysis and robust regression, the so-called Generalized Linear Models (GLMs). In this paper -- the first in a series aimed at illustrating the power of these methods in astronomical applications -- we elucidate the potential of a particular class of GLMs for handling binary/binomial data, the so-called logit and probit regression techniques, from both a maximum likelihood and a Bayesian perspective. As a case in point, we present the use of these GLMs to explore the conditions of star formation activity and metal enrichment in primordial minihaloes from cosmological hydro-simulations including detailed chemistry, gas physics, and stellar feedback. We predict that for a dark mini-halo with metallicity $\approx 1.3 \times 10^{-4} Z_{\bigodot}$, an increase of $1.2 \times 10^{-2}$ in the gas molecular fraction, increases the probability of star formation occurrence by a factor of 75%. Finally, we highlight the use of receiver operating characteristic curves as a diagnostic for binary classifiers, and ultimately we use these to demonstrate the competitive predictive performance of GLMs against the popular technique of artificial neural networks.Comment: 20 pages, 10 figures, 3 tables, accepted for publication in Astronomy and Computin

The Overlooked Potential of Generalized Linear Models in Astronomy-III: Bayesian Negative Binomial Regression and Globular Cluster Populations

In this paper, the third in a series illustrating the power of generalized linear models (GLMs) for the astronomical community, we elucidate the potential of the class of GLMs which handles count data. The size of a galaxy's globular cluster population $N_{\rm GC}$ is a prolonged puzzle in the astronomical literature. It falls in the category of count data analysis, yet it is usually modelled as if it were a continuous response variable. We have developed a Bayesian negative binomial regression model to study the connection between $N_{\rm GC}$ and the following galaxy properties: central black hole mass, dynamical bulge mass, bulge velocity dispersion, and absolute visual magnitude. The methodology introduced herein naturally accounts for heteroscedasticity, intrinsic scatter, errors in measurements in both axes (either discrete or continuous), and allows modelling the population of globular clusters on their natural scale as a non-negative integer variable. Prediction intervals of 99% around the trend for expected $N_{\rm GC}$comfortably envelope the data, notably including the Milky Way, which has hitherto been considered a problematic outlier. Finally, we demonstrate how random intercept models can incorporate information of each particular galaxy morphological type. Bayesian variable selection methodology allows for automatically identifying galaxy types with different productions of GCs, suggesting that on average S0 galaxies have a GC population 35% smaller than other types with similar brightness.Comment: 14 pages, 12 figures. Accepted for publication in MNRA

Transnormativity in the psy disciplines: Constructing pathology in the Diagnostic and Statistical Manual and Standards of Care

The psy disciplines (i.e., psychiatry, psychology, psychoanalysis, and psychotherapy) have played a significant role in shaping understandings of transgender people’s lives in ways that are transnormative (i.e., by emphasizing one particular account of what it means to be transgender). This paper documents 1) how the rise of the psy disciplines created opportunities for transgender people to access treatment (but that such access often required tacit acceptance of transnormativity), and 2) how transgender people have resisted transnormative accounts within the psy disciplines. More specifically, this paper explores how both the American Psychiatric Association’s Diagnostic and Statistical Manual, and what is now the World Professional Association for Transgender Health’s Standards of Care, have often enshrined highly regulatory accounts of transgender people’s lives, while also changing over time, in part due to the contributions of transgender people. The paper concludes by considering recent contributions by transgender people in terms of the use of informed consent models of care and clinical research, and highlights the ongoing marginalization of transgender people in terms of access to ethical, trans-competent care

Medical uncertainty and reproduction of the “normal”: Decision-making around testosterone therapy in transgender pregnancy

In this work, we draw upon in-depth interview and focus group data from a three-year international study of 70 trans people (residing across Australia, Canada, the European Union, United Kingdom, and the United States) about their intentions and experiences around pregnancy, as well as 22 health care providers (practicing across Australia, Canada, the European Union, the United Kingdom, and the United States) with self-identified experience working with trans patients and pregnancy along a diverse cross-section of specialty areas (e.g., psychotherapists, general practitioners, endocrinologists, midwives, lactation consultants, OBGYNs, fertility specialists). The central motivating questions guiding the present work are: 1) For trans people who are taking testosterone, what is the medical advice and guidance around stopping or pausing testosterone therapy to become pregnant, throughout pregnancy, and during the postpartum period (particularly in the context of chestfeeding/breastfeeding); 2) What is the evidence base in the medical empirical literature for this guidance; and 3) How do trans people respond to this guidance

Worth a Glance: Using Eye Movements to Investigate the Cognitive Neuroscience of Memory

Results of several investigations indicate that eye movements can reveal memory for elements of previous experience. These effects of memory on eye movement behavior can emerge very rapidly, changing the efficiency and even the nature of visual processing without appealing to verbal reports and without requiring conscious recollection. This aspect of eye movement based memory investigations is particularly useful when eye movement methods are used with special populations (e.g., young children, elderly individuals, and patients with severe amnesia), and also permits use of comparable paradigms in animals and humans, helping to bridge different memory literatures and permitting cross-species generalizations. Unique characteristics of eye movement methods have produced findings that challenge long-held views about the nature of memory, its organization in the brain, and its failures in special populations. Recently, eye movement methods have been successfully combined with neuroimaging techniques such as fMRI, single-unit recording, and magnetoencephalography, permitting more sophisticated investigations of memory. Ultimately, combined use of eye-tracking with neuropsychological and neuroimaging methods promises to provide a more comprehensive account of brain–behavior relationships and adheres to the “converging evidence” approach to cognitive neuroscience

The String Calculation of QCD Wilson Loops on Arbitrary Surfaces

Compact string expressions are found for non-intersecting Wilson loops in SU(N) Yang-Mills theory on any surface (orientable or nonorientable) as a weighted sum over covers of the surface. All terms from the coupled chiral sectors of the 1/N expansion of the Wilson loop expectation values are included.Comment: 10 pages, LaTeX, no figure

Possible scale invariant linear magnetoresistance in pyrochlore iridates Bi2Ir2O7

We report the observation of a linear magnetoresistance in single crystals and epitaxial thin films of the pyrochlore iridate Bi2Ir2O7. The linear magnetoresistance is positive and isotropic at low temperatures, without any sign of saturation up to 35 T. As temperature increases, the linear field dependence gradually evolves to a quadratic field dependence. The temperature and field dependence of magnetoresistance of Bi2Ir2O7 bears strikingly resemblance to the scale invariant magnetoresistance observed in the strange metal phase in high Tc cuprates. However, the residual resistivity of Bi2Ir2O7 is more than two orders of magnitude higher than the curpates. Our results suggest that the correlation between linear magnetoresistance and quantum fluctuations may exist beyond high temperature superconductors