The neutron and its role in cosmology and particle physics

Experiments with cold and ultracold neutrons have reached a level of precision such that problems far beyond the scale of the present Standard Model of particle physics become accessible to experimental investigation. Due to the close links between particle physics and cosmology, these studies also permit a deep look into the very first instances of our universe. First addressed in this article, both in theory and experiment, is the problem of baryogenesis ... The question how baryogenesis could have happened is open to experimental tests, and it turns out that this problem can be curbed by the very stringent limits on an electric dipole moment of the neutron, a quantity that also has deep implications for particle physics. Then we discuss the recent spectacular observation of neutron quantization in the earth's gravitational field and of resonance transitions between such gravitational energy states. These measurements, together with new evaluations of neutron scattering data, set new constraints on deviations from Newton's gravitational law at the picometer scale. Such deviations are predicted in modern theories with extra-dimensions that propose unification of the Planck scale with the scale of the Standard Model ... Another main topic is the weak-interaction parameters in various fields of physics and astrophysics that must all be derived from measured neutron decay data. Up to now, about 10 different neutron decay observables have been measured, much more than needed in the electroweak Standard Model. This allows various precise tests for new physics beyond the Standard Model, competing with or surpassing similar tests at high-energy. The review ends with a discussion of neutron and nuclear data required in the synthesis of the elements during the "first three minutes" and later on in stellar nucleosynthesis.Comment: 91 pages, 30 figures, accepted by Reviews of Modern Physic

Multi-Phase US Spread and Habitat Switching of a Post-Columbian Invasive, \u3ci\u3eSorghum halepense\u3c/i\u3e

Johnsongrass (Sorghum halepense) is a striking example of a post-Columbian founder event. This natural experiment within ecological time-scales provides a unique opportunity for understanding patterns of continent-wide genetic diversity following range expansion. Microsatellite markers were used for population genetic analyses including leaf-optimized Neighbor-Joining tree, pairwise FST, mismatch analysis, principle coordinate analysis, Tajima\u27s D, Fu\u27s F and Bayesian clusterings of population structure. Evidence indicates two geographically distant introductions of divergent genotypes, which spread across much of the US ingeophylogeny, gene flow patterns can be inferred to have involved five phases. Centers of genetic diversity have shifted from two introduction sites separated by ~2000 miles toward the middle of the range, consistent with admixture between genotypes from the respective introductions. Genotyping provides evidence for a `habitat switch\u27 from agricultural to non-agricultural systems and may contribute to both Johnsongrass ubiquity and aggressiveness. Despite lower and more structured diversity at the invasion front, Johnsongrass continues to advance northward into cooler and drier habitats. Association genetic approaches may permit identification of alleles contributing to the habitat switch or other traits important to weed/invasive management and/or crop improvement

Multi-Phase US Spread and Habitat Switching of a Post-Columbian Invasive, <i>Sorghum halepense</i>

<div><p>Johnsongrass (<i>Sorghum halepense</i>) is a striking example of a post-Columbian founder event. This natural experiment within ecological time-scales provides a unique opportunity for understanding patterns of continent-wide genetic diversity following range expansion. Microsatellite markers were used for population genetic analyses including leaf-optimized Neighbor-Joining tree, pairwise FST, mismatch analysis, principle coordinate analysis, Tajima’s D, Fu’s F and Bayesian clusterings of population structure. Evidence indicates two geographically distant introductions of divergent genotypes, which spread across much of the US in <200 years. Based on geophylogeny, gene flow patterns can be inferred to have involved five phases. Centers of genetic diversity have shifted from two introduction sites separated by ~2000 miles toward the middle of the range, consistent with admixture between genotypes from the respective introductions. Genotyping provides evidence for a ‘habitat switch’ from agricultural to non-agricultural systems and may contribute to both Johnsongrass ubiquity and aggressiveness. Despite lower and more structured diversity at the invasion front, Johnsongrass continues to advance northward into cooler and drier habitats. Association genetic approaches may permit identification of alleles contributing to the habitat switch or other traits important to weed/invasive management and/or crop improvement.</p></div

BAPS6 geographical clustering using Voronoi tesellations and bar representations of genotypes at three K values based on population averages (K = 2, 5, 15).

<p>State boundaries overlaid for K = 15 for visual guidance. Clustering based on individual genotypes (lower bars) is included for K = 15. The two parental species <i>Sorghum bicolor</i> and <i>Sorghum propinquum</i> are labeled as PAR.</p

Saturation plot of <i>Sorghum halepense</i> genotypes after STRUCTURE runs based on Evanno Method (top).

<p>K values reach an asymptote between 15 and 26. DISTRUCT bar graph visualization of results after permuted by CLUMPP at four different K cluster assumptions (K = 2, 5, 15, 26). Clustering based on population averages (lower bars) and individual genotypes (upper bars). The two parental species <i>Sorghum bicolor</i> and <i>Sorghum propinquum</i> are labeled as PAR.</p

Map of sampling sites and N-J tree with an optimized leaf ordering along east–west geographical axis for <i>Sorghum halepense</i> genotypes.

<p>One of the progenitor species, <i>S</i>. <i>propinquum</i>, is used as outgroup. Colonization is outlined in 5 phases (P1-P5). Major gene flow pathways are shown using arrows in four colors (red, green, blue, gray). Initial colonization from southeastern US starting from SC (red arrows) are followed by the second introduction from AZ (S2, S4 green arrows). Gene flow from TX into NM, GA and VA (P3, blue arrows) happens concurrent with local gene flow among GA-AL-SC (P3 arrows not shown for clarity). From CA, there is a massive eastward radiation into NE, KY, FL and VA (P5a, gray arrows). While there is no detectable gene flow among KS, NE and TX (P5c) there is southbound gene flow from NE to FL (S5c, gray arrow) and KS into AL and GA (P5c, arrows not shown for clarity).</p

Contingency table showing observed frequency of <i>Sorghum halepense</i> accessions belonging to each genetic cluster, found in each habitat type (Χ² = 121.79; df = 12; P < 0.0001).

<p>Contingency table showing observed frequency of <i>Sorghum halepense</i> accessions belonging to each genetic cluster, found in each habitat type (Χ² = 121.79; df = 12; P < 0.0001).</p

Multi-Phase US Spread and Habitat Switching of a Post-Columbian Invasive, <i>Sorghum halepense</i> - Fig 2

<p><b>(a)</b> Pairwise comparisons of Nei’s distances (net and raw distances) among (lower/upper diagonal) and within (along diagonal) <i>Sorghum halepense</i> populations. <b>(b)</b> Pairwise comparisons of Fst among populations. Populations diverge as they get farther away from GA and TX. The two progenitor genotypes <i>S</i>. <i>propinquum</i>, <i>S</i>. <i>bicolor</i> and the laboratory standard <i>S</i>. <i>halepense</i> are grouped as PBH.</p

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