160 research outputs found
Political Affiliation of College Youth
Sampling of ISU students shows 35 percent regard themselves as Independents, 33 percent Republicans, 31 percent Democrats. Parental affiliation and class background are important influences
Iowa County Government Reorganization - Pros and Cons
Proponents believe county government reorganization would bring greater efficiency and lower local government costs. Opponents fear reduction in grass roots control of local services
Twirling and Whirling: Viscous Dynamics of Rotating Elastica
Motivated by diverse phenomena in cellular biophysics, including bacterial
flagellar motion and DNA transcription and replication, we study the overdamped
nonlinear dynamics of a rotationally forced filament with twist and bend
elasticity. Competition between twist injection, twist diffusion, and writhing
instabilities is described by a novel pair of coupled PDEs for twist and bend
evolution. Analytical and numerical methods elucidate the twist/bend coupling
and reveal two dynamical regimes separated by a Hopf bifurcation: (i)
diffusion-dominated axial rotation, or twirling, and (ii) steady-state
crankshafting motion, or whirling. The consequences of these phenomena for
self-propulsion are investigated, and experimental tests proposed.Comment: To be published in Physical Review Letter
Transition state theory for laser-driven reactions
This is a pre-print.Recent developments in Transition State Theory brought about by dynamical systems theory
are extended to time-dependent systems such as laser-driven reactions. Using time-dependent
normal form theory, we construct a reaction coordinate with regular dynamics inside the transition
region. The conservation of the associated action enables one to extract time-dependent invariant
manifolds that act as separatrices between reactive and non-reactive trajectories and thus make it
possible to predict the ultimate fate of a trajectory. We illustrate the power of our approach on
a driven H´enon-Heiles system, which serves as a simple example of a reactive system with several
open channels. The present generalization of Transition State Theory to driven systems will allow
one to study processes such as the control of chemical reactions through laser pulses
Needs, trends, and advances in scintillators for radiographic imaging and tomography
Scintillators are important materials for radiographic imaging and tomography
(RadIT), when ionizing radiations are used to reveal internal structures of
materials. Since its invention by R\"ontgen, RadIT now come in many modalities
such as absorption-based X-ray radiography, phase contrast X-ray imaging,
coherent X-ray diffractive imaging, high-energy X- and ray radiography
at above 1 MeV, X-ray computed tomography (CT), proton imaging and tomography
(IT), neutron IT, positron emission tomography (PET), high-energy electron
radiography, muon tomography, etc. Spatial, temporal resolution, sensitivity,
and radiation hardness, among others, are common metrics for RadIT performance,
which are enabled by, in addition to scintillators, advances in high-luminosity
accelerators and high-power lasers, photodetectors especially CMOS pixelated
sensor arrays, and lately data science. Medical imaging, nondestructive
testing, nuclear safety and safeguards are traditional RadIT applications.
Examples of growing or emerging applications include space, additive
manufacturing, machine vision, and virtual reality or `metaverse'. Scintillator
metrics such as light yield and decay time are correlated to RadIT metrics.
More than 160 kinds of scintillators and applications are presented during the
SCINT22 conference. New trends include inorganic and organic scintillator
heterostructures, liquid phase synthesis of perovskites and m-thick films,
use of multiphysics models and data science to guide scintillator development,
structural innovations such as photonic crystals, nanoscintillators enhanced by
the Purcell effect, novel scintillator fibers, and multilayer configurations.
Opportunities exist through optimization of RadIT with reduced radiation dose,
data-driven measurements, photon/particle counting and tracking methods
supplementing time-integrated measurements, and multimodal RadIT.Comment: 45 pages, 43 Figures, SCINT22 conference overvie
Association Between Whole Blood-Derived Mitochondrial Dna Copy Number, Low-Density Lipoprotein Cholesterol, and Cardiovascular Disease Risk
Background The relationship between mitochondrial DNA copy number (mtDNA CN) and cardiovascular disease remains elusive. Methods and Results We performed cross-sectional and prospective association analyses of blood-derived mtDNA CN and cardiovascular disease outcomes in 27 316 participants in 8 cohorts of multiple racial and ethnic groups with whole-genome sequencing. We also performed Mendelian randomization to explore causal relationships of mtDNA CN with coronary heart disease (CHD) and cardiometabolic risk factors (obesity, diabetes, hypertension, and hyperlipidemia)
Climate Change and the Future of California's Endemic Flora
The flora of California, a global biodiversity hotspot, includes 2387 endemic plant taxa. With anticipated climate change, we project that up to 66% will experience >80% reductions in range size within a century. These results are comparable with other studies of fewer species or just samples of a region's endemics. Projected reductions depend on the magnitude of future emissions and on the ability of species to disperse from their current locations. California's varied terrain could cause species to move in very different directions, breaking up present-day floras. However, our projections also identify regions where species undergoing severe range reductions may persist. Protecting these potential future refugia and facilitating species dispersal will be essential to maintain biodiversity in the face of climate change
The genetic determinants of recurrent somatic mutations in 43,693 blood genomes
Nononcogenic somatic mutations are thought to be uncommon and inconsequential. To test this, we analyzed 43,693 National Heart, Lung and Blood Institute Trans-Omics for Precision Medicine blood whole genomes from 37 cohorts and identified 7131 non-missense somatic mutations that are recurrently mutated in at least 50 individuals. These recurrent non-missense somatic mutations (RNMSMs) are not clearly explained by other clonal phenomena such as clonal hematopoiesis. RNMSM prevalence increased with age, with an average 50-year-old having 27 RNMSMs. Inherited germline variation associated with RNMSM acquisition. These variants were found in genes involved in adaptive immune function, proinflammatory cytokine production, and lymphoid lineage commitment. In addition, the presence of eight specific RNMSMs associated with blood cell traits at effect sizes comparable to Mendelian genetic mutations. Overall, we found that somatic mutations in blood are an unexpectedly common phenomenon with ancestry-specific determinants and human health consequences
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