2,925 research outputs found
Strategic Factors in Nineteenth Century American Economic History: A Volume to Honor Robert W. Fogel
Virtual Betti numbers of genus 2 bundles
We show that if M is a surface bundle over S^1 with fiber of genus 2, then
for any integer n, M has a finite cover tilde(M) with b_1(tilde(M)) > n. A
corollary is that M can be geometrized using only the `non-fiber' case of
Thurston's Geometrization Theorem for Haken manifolds.Comment: Published by Geometry and Topology at
http://www.maths.warwick.ac.uk/gt/GTVol6/paper19.abs.htm
The Association Between Discrimination and Sleep is Exacerbated in Individuals with Comorbid Chronic Health Conditions
Introduction: The consequences of recurrent, stressful daily experiences for sleep health appear intensified in individuals with pre-existing health conditions. Although discrimination has been associated with sleep outcomes, the role of comorbid chronic health conditions (CCHCs), and impact of perceived discrimination, remains unclear. The present study investigated (1) the associations between daily discrimination and sleep and (2) moderating roles of CCHCs and daily life interference and hardship.
Methods: The current study utilized archival data from the Midlife in the United States (MIDUS) Study II. Participants, 174 adults (51% female, Mage=57 yrs., SD=11.5 yrs.), completed 7 days of actigraphy, sleep diary, PSQI, and CCHC-reporting measures. Models examined the moderating effects of CCHCs, daily interference, and hardship on the association between discrimination and sleep.
Results: Daily discriminatory experiences predicted numerous poor sleep outcomes, exacerbated for persons with higher CCHCs. Higher comorbidity (95% CI=5.40, 68.75) exacerbated the association between discrimination and TSTactigraphy, further strengthened by perceived hardship (95% CI=-3.75, -.40) and interference (95% CI=-3.65, -.30). Number of CCHCs, qualified by perceived hardship (95% CI=.00, .04) and interference (95% CI=.01, .05), predicted diary sleep quality above discrimination. The interaction between CCHCs and hardship predicted global PSQI scores (95% CI=-.91, -.12) beyond discrimination.
Conclusion: Daily experiences of discrimination are associated with decreased sleep duration and quality. These associations were stronger for individuals with multiple CCHCs. Exacerbating CCHC effects were perpetuated by perceived interference and hardships, suggesting individual emotion regulation (ER) differences. Future research should attend to sleep-related consequences of differential discrimination-informed ER by persons with CCHCs.https://scholarscompass.vcu.edu/gradposters/1042/thumbnail.jp
Wigner's Friend paradoxes: consistency with weak-contextual and weak-macroscopic realism models
Wigner's friend paradoxes highlight contradictions between measurements made
by Friends inside a laboratory and superobservers outside a laboratory, who
have access to an entangled state of the measurement apparatus. The
contradictions lead to no-go theorems for observer-independent facts, thus
challenging concepts of objectivity. Here, we examine the paradoxes from the
perspective of establishing consistency with macroscopic realism. We present
versions of the Brukner-Wigner-friend and Frauchiger-Renner paradoxes in which
the spin- system measured by the Friends corresponds to two
macroscopically distinct states. The local unitary operations that
determine the measurement setting are carried out using nonlinear
interactions, thereby ensuring measurements need only distinguish between the
macroscopically distinct states. The macroscopic paradoxes are perplexing,
seemingly suggesting there is no objectivity in a macroscopic limit. However,
we demonstrate consistency with a contextual weak form of macroscopic realism
(wMR): The premise wMR asserts that the system can be considered to have a
definite spin outcome , at the time after the system has
undergone the unitary rotation to prepare it in a suitable pointer
basis. We further show that the paradoxical outcomes imply failure of
deterministic macroscopic local realism, and arise when there are unitary
interactions occurring due to a change of measurement setting at
both sites, with respect to the state prepared by each Friend. In models which
validate wMR, there is a breakdown of a subset of the assumptions that
constitute the Bell-Locality premise. A similar interpretation involving a weak
contextual form of realism exists for the original paradoxes
Resilin distribution and sexual dimorphism in the midge antenna and their influence on frequency sensitivity
Small-scale bioacoustic sensors, such as antennae in insects, are often considered, biomechanically, to be not much more than the sum of their basic geometric features. Therefore, little is known about the fine structure and material properties of these sensors—even less so about the degree to which the well-known sexual dimorphism of the insect antenna structure affects those properties. By using confocal laser scanning microscopy (CLSM), we determined material composition patterns and estimated distribution of stiffer and softer materials in the antennae of males and females of the non-biting midge Chironomus riparius. Using finite element modelling (FEM), we also have evidence that the differences in composition of these antennae can influence their mechanical responses. This study points to the possibility that modulating the elastic and viscoelastic properties along the length of the antennae can affect resonant characteristics beyond those expected of simple mass-on-a-spring systems—in this case, a simple banded structure can change the antennal frequency sensitivity. This constitutes a simple principle that, now demonstrated in another Dipteran group, could be widespread in insects to improve various passive and active sensory performances
Epstein - Barr virus latent membrane protein 1 suppresses reporter activity through modulation of promyelocytic leukemia protein-nuclear bodies
The Epstein-Barr virus (EBV) encoded Latent Membrane Protein 1 (LMP1) has been shown to increase the expression of promyelocytic leukemia protein (PML) and the immunofluorescent intensity of promyelocytic leukemia nuclear bodies (PML NBs). PML NBs have been implicated in the modulation of transcription and the association of reporter plasmids with PML NBs has been implicated in repression of reporter activity. Additionally, repression of various reporters in the presence of LMP1 has been noted. This study demonstrates that LMP1 suppresses expression of reporter activity in a dose responsive manner and corresponds with the LMP1 induced increase in PML NB intensity. Disruption of PML NBs with arsenic trioxide or a PML siRNA restores reporter activity. These data offer an explanation for previously conflicting data on LMP1 signaling and calls attention to the possibility of false-positives and false-negatives when using reporter assays as a research tool in cells expressing LMP1
The Nature of Associated Absorption and the UV-X-ray Connection in 3C 288.1
We discuss new Hubble Space Telescope spectroscopy of the radio-loud quasar,
3C 288.1. The data cover ~590 A to ~1610 A in the quasar rest frame. They
reveal a wealth of associated absorption lines (AALs) with no accompanying
Lyman-limit absorption. The metallic AALs range in ionization from C III and N
III to Ne VIII and Mg X. We use these data and photoionization models to derive
the following properties of the AAL gas: 1) There are multiple ionization zones
within the AAL region, spanning a factor of at least ~50 in ionization
parameter. 2) The overall ionization is consistent with the ``warm'' X-ray
continuum absorbers measured in Seyfert 1 nuclei and other QSOs. However, 3)
the column densities implied by the AALs in 3C 288.1 are too low to produce
significant bound-free absorption at any UV-X-ray wavelengths. Substantial
X-ray absorption would require yet another zone, having a much higher
ionization or a much lower velocity dispersion than the main AAL region. 4) The
total hydrogen column density in the AAL gas is log N_H (cm-2)= 20.2. 5) The
metallicity is roughly half solar. 6) The AALs have deconvolved widths of ~900
km/s and their centroids are consistent with no shift from the quasar systemic
velocity (conservatively within +/-1000 km/s). 7) There are no direct
indicators of the absorber's location in our data, but the high ionization and
high metallicity both suggest a close physical relationship to the quasar/host
galaxy environment. Finally, the UV continuum shape gives no indication of a
``blue bump'' at higher energies. There is a distinct break of unknown origin
at ~1030 A, and the decline toward higher energies (with spectral index alpha =
-1.73, for f_nu ~ nu^alpha) is even steeper than a single power-law
interpolation from 1030 A to soft X-rays.Comment: 27 pages with figures and tables, in press with Ap
Developing a Novel Platform for Characterizing Thermoelectric Materials for Uncooled Detectors for Land Imaging Applications
Thermal land imaging (imaging at ~8-14 micron optical wavelength) is an essential tool for understanding and managing terrestrial freshwater resources. Current thermal imaging instruments employ low temperature detectors, which require cryocoolers. Consequently, cost-saving reductions in size, weight, and power can be achieved by employing uncooled detectors. One uncooled detector concept, which NASA is pursuing, is a thermopile detector with sub-micron thick doped-Si thermoelectric materials. In order to characterize the thermoelectric properties of the doped silicon, we designed and optimized a novel apparatus. This simple apparatus measures the Seebeck coefficient with thermally isolated stages and LABVIEW automation. We optimized thermal stability using PID tuning and optimized the thermal contact between the thin film samples and stages using electrically conductive springs. Utilizing our apparatus, we measured the Seebeck coefficient of 0.45 micron thick phosphorus-doped single crystal Si samples bonded to alumina substrates. Using these Seebeck coefficient measurements and four-wire electrical resistivity measurements, we determined the relationship between the thermoelectric figure of merit and dopant concentration. These characterization results for doped-Si will guide our thermopile detector design to provide an optimal and competitive detector alternative for future thermal imaging instruments
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