Brain Specificity of Diffuse Optical Imaging: Improvements from Superficial Signal Regression and Tomography

Functional near infrared spectroscopy (fNIRS) is a portable monitor of cerebral hemodynamics with wide clinical potential. However, in fNIRS, the vascular signal from the brain is often obscured by vascular signals present in the scalp and skull. In this paper, we evaluate two methods for improving in vivo data from adult human subjects through the use of high-density diffuse optical tomography (DOT). First, we test whether we can extend superficial regression methods (which utilize the multiple source–detector pair separations) from sparse optode arrays to application with DOT imaging arrays. In order to accomplish this goal, we modify the method to remove physiological artifacts from deeper sampling channels using an average of shallow measurements. Second, DOT provides three-dimensional image reconstructions and should explicitly separate different tissue layers. We test whether DOT's depth-sectioning can completely remove superficial physiological artifacts. Herein, we assess improvements in signal quality and reproducibility due to these methods using a well-characterized visual paradigm and our high-density DOT system. Both approaches remove noise from the data, resulting in cleaner imaging and more consistent hemodynamic responses. Additionally, the two methods act synergistically, with greater improvements when the approaches are used together

sMILES: A Library of Semi-Empirical MILES Stellar Spectra with Variable [α/Fe] Abundances

We present a new library of semi-empirical stellar spectra that is based on the empirical MILES library. A new, high resolution library of theoretical stellar spectra is generated that is specifically designed for use in stellar population studies. We test these models across their full wavelength range against other model libraries and find reasonable agreement in their predictions of spectral changes due to atmospheric α-element variations, known as differential corrections. We also test the models against the MILES and MaStar libraries of empirical stellar spectra and also find reasonable agreements, as expected from previous work. We then use the abundance pattern predictions of the new theoretical stellar spectra to differentially correct MILES spectra to create semi-empirical MILES (sMILES) star spectra with abundance patterns that differ from those present in the Milky Way. The final result is 5 families of 801 sMILES stars with [α/Fe] abundances ranging from −0.20 to 0.60 dex at MILES resolution (FWHM=2.5 Å) and wavelength coverage (3540.5 − 7409.6 Å). We make the sMILES library publicly available

Mobility and the making of the neoliberal “creative city”: The streetcar as a creative city project?

In recent years, there has been a remarkable rebirth of the streetcar in cities throughout the United States, with dozens of projects under consideration, in planning and construction, or already completed in cities throughout the country. Building on transport geography research on the streetcar, urban studies contributions on neoliberal urbanization and the creative city, and insights from the new mobilities paradigm, this paper sets out to investigate the broad political − economic logic driving this nationwide development trend. Based predominantly on a qualitative content analysis of selected project documents from 12 streetcar projects, I find that the reemergence of these streetcar projects in recent years reflects and is embedded in the general trajectory of neoliberal urbanization and can more precisely be understood as a creative city development tool

Recommitting to the car? The politics of multimodal transportation in Wisconsin

In this dissertation research, I investigate two cases which exemplify a larger politics of multimodal transportation in Wisconsin: the 2010 Wisconsin high-speed rail (HSR) debate; and the 2011 debate over whether to add a bike path to Milwaukee's Hoan Bridge during its redecking. In both case studies, I trace the politics of these projects, and investigate how the decisions not to pursue these projects came to be legitimized. I approach these case studies using a transportation-focused politics of mobility framework, located at the intersection of transportation geography and new mobilities paradigm scholarship. Employing a range of qualitative methods, I find that not only were certain stakeholders (such as newly-elected politicians in state government, and Department of Transportation officials) significant in making decisions against these projects, but the way that transportation was thought about among the general public in Wisconsin served to legitimize the end of these projects. In the case of Wisconsin HSR, the original contribution I make is to demonstrate how the manner in which Wisconsin HSR was spatially conceptualized in the debate was ultimately significant for how the decision to abandon the project came to make logical sense to a majority of Wisconsin residents. Further, this case study contributes original insights into the meanings that HSR had for people in Wisconsin, which serves as a caution against overly rigid, national-scale explanations of why the project failed. In the case of the Hoan Bridge bike path, the original contribution is to empirically demonstrate how the tools of traffic engineering have embedded within them particular visions of how mobility and its spaces ought to be, and that this embedded bias can be concealed by claiming that such tools are scientific, and by implication, value-free. In addition to revealing this embedded bias, the case study demonstrates that the representation of these tools to the general public can be political. Taken together, these case studies suggest that productive work can be done at the intersection of transportation geography and mobilities research by using this politics of mobility framework. Further, these case studies underline the fact that debates over transportation involve a range of competing interests, beliefs, normative values, and meanings that are bound up with transportation, and that these aspects deserve greater attention in transportation geography and mobilities research

Neonatal hemodynamic response to visual cortex activity: high-density near-infrared spectroscopy study

The neurodevelopmental outcome of neonatal intensive care unit (NICU) infants is a major clinical concern with many infants displaying neurobehavioral deficits in childhood. Functional neuroimaging may provide early recognition of neural deficits in high-risk infants. Near-infrared spectroscopy (NIRS) has the advantage of providing functional neuroimaging in infants at the bedside. However, limitations in traditional NIRS have included contamination from superficial vascular dynamics in the scalp. Furthermore, controversy exists over the nature of normal vascular, responses in infants. To address these issues, we extend the use of novel high-density NIRS arrays with multiple source-detector distances and a superficial signal regression technique to infants. Evaluations of healthy term-born infants within the first three days of life are performed without sedation using a visual stimulus. We find that the regression technique significantly improves brain activation signal quality. Furthermore, in six out of eight infants, both oxy- and total hemoglobin increases while deoxyhemoglobin decreases, suggesting that, at term, the neurovascular coupling in the visual cortex is similar to that found in healthy adults. These results demonstrate the feasibility of using high-density NIRS arrays in infants to improve signal quality through superficial signal regression, and provide a foundation for further development of high-density NIRS as a clinical tool