137 research outputs found
Collision statistics of driven granular materials
We present an experimental investigation of the statistical properties of
spherical granular particles on an inclined plane that are excited by an
oscillating side-wall. The data is obtained by high-speed imaging and particle
tracking techniques. We identify all particles in the system and link their
positions to form trajectories over long times. Thus, we identify particle
collisions to measure the effective coefficient of restitution and find a broad
distribution of values for the same impact angles. We find that the energy
inelasticity can take on values greater than one, which implies that the
rotational degrees play an important role in energy transfer. We also measure
the distance and the time between collision events in order to directly
determine the distribution of path lengths and the free times. These
distributions are shown to deviate from expected theoretical forms for elastic
spheres, demonstrating the inherent clustering in this system. We describe the
data with a two-parameter fitting function and use it to calculated the mean
free path and collision time. We find that the ratio of these values is
consistent with the average velocity. The velocity distribution are observed to
be strongly non-Gaussian and do not demonstrate any apparent universal
behavior. We report the scaling of the second moment, which corresponds to the
granular temperature, and higher order moments as a function of distance from
the driving wall. Additionally, we measure long time correlation functions in
both space and in the velocities to probe diffusion in a dissipative gas.Comment: 12 pages, 4 figures, uses revtex
The Potential for Neutrino Physics at Muon Colliders and Dedicated High Current Muon Storage Rings
Conceptual design studies are underway for muon colliders and other
high-current muon storage rings that have the potential to become the first
true ``neutrino factories''. Muon decays in long straight sections of the
storage rings would produce precisely characterized beams of electron and muon
type neutrinos of unprecedented intensity. This article reviews the prospects
for these facilities to greatly extend our capabilities for neutrino
experiments, largely emphasizing the physics of neutrino interactions.Comment: 107 pages, 16 figures, to be published in Physics Report
Mendelian randomization implies no direct causal association between leukocyte telomere length and amyotrophic lateral sclerosis
Funder: QingLan Research Project of Jiangsu for Outstanding Young TeachersFunder: Project funded by Postdoctoral Science Foundation of Xuzhou Medical UniversityFunder: Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD) for Xuzhou Medical UniversityAbstract: We employed Mendelian randomization (MR) to evaluate the causal relationship between leukocyte telomere length (LTL) and amyotrophic lateral sclerosis (ALS) with summary statistics from genome-wide association studies (n = ~ 38,000 for LTL and ~ 81,000 for ALS in the European population; n = ~ 23,000 for LTL and ~ 4,100 for ALS in the Asian population). We further evaluated mediation roles of lipids in the pathway from LTL to ALS. The odds ratio per standard deviation decrease of LTL on ALS was 1.10 (95% CI 0.93–1.31, p = 0.274) in the European population and 0.75 (95% CI 0.53–1.07, p = 0.116) in the Asian population. This null association was also detected between LTL and frontotemporal dementia in the European population. However, we found that an indirect effect of LTL on ALS might be mediated by low density lipoprotein (LDL) or total cholesterol (TC) in the European population. These results were robust against extensive sensitivity analyses. Overall, our MR study did not support the direct causal association between LTL and the ALS risk in neither population, but provided suggestive evidence for the mediation role of LDL or TC on the influence of LTL and ALS in the European population
- …