The roles of inter- and intra-sexual selection in behavioral isolation between native and invasive pupfishes

Male-male competition and female mate choice may both play important roles in driving and maintaining reproductive isolation between species. When previously allopatric species come into secondary contact with each other due to introductions, they provide an opportunity to evaluate the identity and strength of reproductive isolating mechanisms. If reproductive isolation is not maintained, hybridization may occur. We examined how reproductive isolating mechanisms mediate hybridization between endemic populations of the Red River pupfish Cyprinodon rubrofluviatilis and the recently introduced sheepshead minnow C. variegatus. In lab-based dominance trials, males of both species won the same number of competitions. However, male C. rubrofluviatilis that won competitions were more aggressive than C. variegatus winners, and more aggression was needed to win against competitor C. variagatus than allopatric C. rubrofluviatilis. Duration of fights also differed based on the relatedness of the competitor. In dichotomous mate choice trials, there were no conspecific or heterospecific preferences expressed by females of either species. Our findings that male-male aggression differs between closely and distantly related groups, but female choice does not suggest that male-male competition may be the more likely mechanism to impede gene flow in this system

Quantum Logic Gates and Nuclear Magnetic Resonance Pulse Sequences

We demonstrate how NMR can in principle be used to implement all the elements required to build quantum computers, and briefly discuss the potential applications of insights from quantum logic to the development of novel pulse sequences with applications in more conventional NMR experiments.Comment: Sixteen pages, no figures. Submitted to Journal of Magnetic Resonance. Primarily pedagogical rather than a description of novel research result

DESIGN AND PERFORMANCE OF STRETCHABLE THERMOELECTRIC NANOWIRE COMPOSITES

Thermoelectric materials efficiently and directly convert waste heat into electricity, enabling new engineering applications ranging from micro scale solid-state cooling in computers to clean energy harvesting and conversion. For example, thermoelectric alloys have been useful for past NASA missions in deep-space exploration outside the solar system, where traditional solar cells cannot function properly due to the lack of light. NASA uses radioisotope thermoelectric generators on satellites, taking the hot particles from the decay of a radioactive isotope, to heat thermoelectric alloy coatings that generate electricity. The problem with these alloy coating materials, however, stems from their poor mechanical strength. They are generally brittle and break under very small elastic deformation, which makes their integration to curved surfaces or soft fabrics impossible. This study presents optimal conditions to control the growth and harvesting of the nanowires to achieve longer lengths in order to increase conductivity, a substrate that is flexible and stretchable enough, but also strong enough to be considered for wearable electronics, and the mechanical performance of newly-developed flexible polymer composites containing a dense network of thermoelectric alloy nanowires with a diameter less than 200 nm. Further research on such elastically-compliant nanowire-based composite materials could lead to significant technological breakthroughs such as enabling computers to be integrated into clothing, powered by body heat, or cutting down on waste energy from excess heat by wrapping them around hot exhausts and engines to power electrical devices

Precision measurement and symmetry properties of metastable hydrogen

Includes bibliographical references.2022 Fall.Hydrogen has been an indispensable system to study during the development of quantum mechanics due to the simplicity of its atomic structure. Hydrogen maintains its utility today as an important tool for determining fundamental values such as the Rydberg and fine structure constants, as well as the proton charge radius. The work described in this thesis aims to use hydrogen for determining the proton Zemach radius, to search for anomalous spin-dependent forces, and to provide means for measuring the degree of parity violation within this simple system. An overview of a 2S1/2 hyperfine interval measurement is described, followed by a description of the apparatus used and finally a discussion of the systematic effects to be characterized. A proposed parity violation experiment is also described

A Bayesian treatment of the German tank problem

The German tank problem has an interesting historical background and is an engaging problem of statistical estimation for the classroom. The objective is to estimate the size of a population of tanks inscribed with sequential serial numbers, from a random sample. In this tutorial article, we outline the Bayesian approach to the German tank problem, (i) whose solution assigns a probability to each tank population size, thereby quantifying uncertainty, and (ii) which provides an opportunity to incorporate prior information and/or beliefs about the tank population size into the solution. We illustrate with an example. Finally, we survey problems in other contexts that resemble the German tank problem.Comment: - fix eqn. 16 which should start at n'=k, not n'=0. - small tuning of writing. - make x-axis labels in Fig. 1 exactly consistent wordin