Path integral Monte Carlo simulation of global and local superfluidity in liquid 4^{4}He reservoirs separated by nanoscale apertures

We present a path integral Monte Carlo study of the global superfluid fraction and local superfluid density in cylindrically-symmetric reservoirs of liquid $^{4}$He separated by nanoaperture arrays. The superfluid response to both translations along the axis of symmetry (longitudinal response) and rotations about the cylinder axis (transverse response) are computed, together with radial and axial density distributions that reveal the microscopic inhomogeneity arising from the combined effects of the confining external potential and the $^4$He-$^4$He interatomic potentials. We make a microscopic determination of the length-scale of decay of superfluidity at the radial boundaries of the system by analyzing the local superfluid density distribution to extract a displacement length that quantifies the superfluid mass displacement away from the boundary. We find that the longitudinal superfluid response is reduced in reservoirs separated by a septum containing sufficiently small apertures compared to a cylinder with no intervening aperture array, for all temperatures below $T_{\lambda}$. For a single aperture in the septum, a significant drop in the longitudinal superfluid response is seen when the aperture diameter is made smaller than twice the empirical temperature-dependent $^4$He healing length, consistent with the formation of a weak link between the reservoirs. Increasing the diameter of a single aperture or the number of apertures in the array results in an increase of the superfluid density toward the expected bulk value.Comment: 12 pages, 6 figure

Responsible Brains: Neuroscience, Law, and Human Culpability

[This download includes the table of contents and chapter 1.] When we praise, blame, punish, or reward people for their actions, we are holding them responsible for what they have done. Common sense tells us that what makes human beings responsible has to do with their minds and, in particular, the relationship between their minds and their actions. Yet the empirical connection is not necessarily obvious. The “guilty mind” is a core concept of criminal law, but if a defendant on trial for murder were found to have serious brain damage, which brain parts or processes would have to be damaged for him to be considered not responsible, or less responsible, for the crime? The authors argue that evidence from neuroscience and the other cognitive sciences can illuminate the nature of responsibility and agency. They go on to offer a novel and comprehensive neuroscientific theory of human responsibility

Torque control system

System stabilizes aximuth of gondolas which are carried by high-altitude balloons as platforms for tracking telescopes. When telescopes must be constantly aimed at specific targets, control system stabilizes gondola to within 5 arc-seconds

Lesbian brides: post-queer popular culture

The last decade has witnessed a proliferation of lesbian representations in European and North American popular culture, particularly within television drama and broader celebrity culture. The abundance of “positive” and “ordinary” representations of lesbians is widely celebrated as signifying progress in queer struggles for social equality. Yet, as this article details, the terms of the visibility extended to lesbians within popular culture often a rm ideals of hetero-patriarchal, white femininity. Focusing on the visual and narrative registers within which lesbian romances are mediated within television drama, this article examines the emergence of what we describe as “the lesbian normal.” Tracking the ways in which the lesbian normal is anchored in a longer history of “the normal gay,” it argues that the lesbian normal is indicative of the emergence of a broader post-feminist and post-queer popular culture, in which feminist and queer struggles are imagined as completed and belonging to the past. Post-queer popular culture is depoliticising in its e ects, diminishing the critical potential of feminist and queer politics, and silencing the actually existing conditions of inequality, prejudice, and stigma that continue to shape lesbian lives

IL-15 sustains IL-7R-independent ILC2 and ILC3 development

The signals that maintain tissue-resident innate lymphoid cells (ILC) in different microenvironments are incompletely understood. Here we show that IL-7 receptor (IL-7R) is not strictly required for the development of any ILC subset, as residual cells persist in the small intestinal lamina propria (siLP) of adult and neonatal Il7ra(−/−) mice. Il7ra(−/−) ILC2 primarily express an ST2(−) phenotype, but are not inflammatory ILC2. CCR6(+) ILC3, which express higher Bcl-2 than other ILC3, are the most abundant subset in Il7ra(−/−) siLP. All ILC subsets are functionally competent in vitro, and are sufficient to provide enhanced protection to infection with C. rodentium. IL-15 equally sustains wild-type and Il7ra(−/−) ILC survival in vitro and compensates for IL-7R deficiency, as residual ILCs are depleted in mice lacking both molecules. Collectively, these data demonstrate that siLP ILCs are not completely IL-7R dependent, but can persist partially through IL-15 signalling

Master of Science

thesisUnderstanding the connection between large-scale meteorology, cloud macrophysical variables, and cloud microphysical variables is needed in order to improve the parameterization of marine boundary layer (MBL) clouds in weather and climate models. For this study, multiple aspects of MBL clouds over the Atmospheric Radiation Measurement Program (ARM) mobile site at Graciosa Island, Azores are examined. Hourly averaged raw variables of cloud fraction, column summed dBZ, liquid water path, first cloud base height, boundary layer static stability, and midtropospheric static stability are clustered together using a K-means clustering algorithm. The cluster output infers seven characteristic cloud regimes that describe the spectrum of warm boundary layer clouds that occurred over Graciosa Island during the deployment. These cloud regimes range from precipitating stratocumulus to nonprecipitating fair weather cumulus to deep clouds associated with broad synoptic scale frontal systems. Using the cluster results and NCEP/NCAR reanalysis, the typical macrophysical and meteorological environments for the MBL cloud regimes are summarized along with their average radar profiles. MBL cloud microphysical properties are then derived using a new retrieval algorithm that assumes the presence of both cloud and precipitation particle modes within a radar resolution volume. Compared to a traditional single mode particle size distribution (PSD), a bimodal PSD is closer to in-situ observations and is expected to provide improved statistics and understanding of the cloud microphysical parameters such as number concentration, precipitation rate, and effective droplet sizes. The bimodal retrieval algorithm can use either ARM ground-based or A-Train satellite-based data as an input. This study finds that ARM and A-Train versions of the bimodal algorithm retrieve plausible microphysics and the reasons for their differences are explored. Case studies are completed using the bimodal retrieval for three shallow cloud regimes with varying precipitation, macrophysical, and synoptic environments. Results show that microphysical quantities do change as the cloud regime varies and validate the connection between the large and small-scale environment of MBL clouds. The specifics of the unique regime-based microphysics are also useful in order to better parameterize these clouds in models

Doctor of Philosophy

dissertationPrevious research documents prominent associations between firm characteristics and the value of corporate cash holdings. Among these associations, the prior literature shows that firm-specific financial constraints influence the value of cash. We extend the prior literature by introducing time-varying aggregate financial constraints. We find that the value of cash holdings is conditional on aggregate funding conditions. Our findings also suggest that the relative outperformance of high cash firms in prior literature is largely, and for certain return metrics entirely, attributable to the relative performance of these firms during constrained funding periods. Additionally, contrary to the prior assertion that cash holdings allow constrained firms to make value-enhancing investments, we find evidence suggesting that during periods of constrained aggregate funding the benefits of cash holdings accrue primarily because they reduce the risk of financial distress