Experimental tests of reaction rate theory: Mu+H2 and Mu+D2

Copyright @ 1987 American Institute of Physics.Bimolecular rate constants for the thermal chemical reactions of muonium (Mu) with hydrogen and deuterium—Mu+H2→MuH+H and Mu+D2→MuD+D—over the temperature range 473–843 K are reported. The Arrhenius parameters and 1σ uncertainties for the H2 reaction are log A (cm3 molecule-1 s-1)=-9.605±0.074 and Ea =13.29±0.22 kcal mol-1, while for D2 the values are -9.67±0.12 and 14.73±0.40, respectively. These results are significantly more precise than those reported earlier by Garner et al. For the Mu reaction with H2 our results are in excellent agreement with the 3D quantum mechanical calculations of Schatz on the Liu–Siegbahn–Truhlar–Horowitz potential surface, but the data for both reactions compare less favorably with variational transition-state theory, particularly at the lower temperatures.NSERC (Canada) and the Petroleum Research Foundation of the Americal Chemical Society

Reaction kinetics of muonium with the halogen gases (F2, Cl2, and Br2)

Copyright @ 1989 American Institute of PhysicsBimolecular rate constants for the thermal chemical reactions of muonium (Mu) with the halogen gases—Mu+X2→MuX+X—are reported over the temperature ranges from 500 down to 100, 160, and 200 K for X2=F2,Cl2, and Br2, respectively. The Arrhenius plots for both the chlorine and fluorine reactions show positive activation energies Ea over the whole temperature ranges studied, but which decrease to near zero at low temperature, indicative of the dominant role played by quantum tunneling of the ultralight muonium atom. In the case of Mu+F2, the bimolecular rate constant k(T) is essentially independent of temperature below 150 K, likely the first observation of Wigner threshold tunneling in gas phase (H atom) kinetics. A similar trend is seen in the Mu+Cl2 reaction. The Br2 data exhibit an apparent negative activation energy [Ea=(−0.095±0.020) kcal mol−1], constant over the temperature range of ∼200–400 K, but which decreases at higher temperatures, indicative of a highly attractive potential energy surface. This result is consistent with the energy dependence in the reactive cross section found some years ago in the atomic beam data of Hepburn et al. [J. Chem. Phys. 69, 4311 (1978)]. In comparing the present Mu data with the corresponding H atom kinetic data, it is found that Mu invariably reacts considerably faster than H at all temperatures, but particularly so at low temperatures in the cases of F2 and Cl2. The current transition state calculations of Steckler, Garrett, and Truhlar [Hyperfine Interact. 32, 779 (986)] for Mu+X2 account reasonably well for the rate constants for F2 and Cl2 near room temperature, but their calculated value for Mu+Br2 is much too high. Moreover, these calculations seemingly fail to account for the trend in the Mu+F2 and Mu+Cl2 data toward pronounced quantum tunneling at low temperatures. It is noted that the Mu kinetics provide a crucial test of the accuracy of transition state treatments of tunneling on these early barrier HX2 potential energy surfaces.NSERC (Canada), Donors of the Petroleum Research Fund, administered by the American Chemical Society, for their partial support of this research and the Canada Council

Absolute differential positronium-formation cross sections

The first absolute experimental determinations of the differential cross-sections for the formation of ground-state positronium are presented for He, Ar, H2 and CO2 near 0○. Results are compared with available theories. The ratio of the differential and integrated cross-sections for the targets exposes the higher propensity for forward-emission of positronium formed from He and H2

Resources and student achievement – evidence from a Swedish policy reform

This paper utilizes a policy change to estimate the effect of teacher density on student performance. We find that an increase in teacher density has a positive effect on student achievement. The baseline estimate – obtained by using the grade point average as the outcome variable – implies that resource increases corresponding to the class-size reduction in the STAR-experiment (i.e., a reduction of 7 students) improves performance by 2.6 percentile ranks (or 0.08 standard deviations). When we use test score data for men, potentially a more objective measure of student performance, the effect of resources appears to be twice the size of the baseline estimate.Student performance; teacher/student ratio; policy reform; differences-in-differences

An Auto-Offset-Removal circuit for chemical sensing based on the PG-ISFET

Published versio

On defining the Hamiltonian beyond quantum theory

Energy is a crucial concept within classical and quantum physics. An essential tool to quantify energy is the Hamiltonian. Here, we consider how to define a Hamiltonian in general probabilistic theories, a framework in which quantum theory is a special case. We list desiderata which the definition should meet. For 3-dimensional systems, we provide a fully-defined recipe which satisfies these desiderata. We discuss the higher dimensional case where some freedom of choice is left remaining. We apply the definition to example toy theories, and discuss how the quantum notion of time evolution as a phase between energy eigenstates generalises to other theories.Comment: Authors' accepted manuscript for inclusion in the Foundations of Physics topical collection on Foundational Aspects of Quantum Informatio

S-, P- and D-wave resonances in positronium-sodium and positronium-potassium scattering

Scattering of positronium (Ps) by sodium and potassium atoms has been investigated employing a three-Ps-state coupled-channel model with Ps(1s,2s,2p) states using a time-reversal-symmetric regularized electron-exchange model potential fitted to reproduce accurate theoretical results for PsNa and PsK binding energies. We find a narrow S-wave singlet resonance at 4.58 eV of width 0.002 eV in the Ps-Na system and at 4.77 eV of width 0.003 eV in the Ps-K system. Singlet P-wave resonances in both systems are found at 5.07 eV of width 0.3 eV. Singlet D-wave structures are found at 5.3 eV in both systems. We also report results for elastic and Ps-excitation cross sections for Ps scattering by Na and K.Comment: 9 pages, 5 figures, Accepted in Journal of Physics

Academic Achievement and School Resources

This chapter examines the national and local trends in educational policy, focusing in particular on Nevada’s academic achievement, standardized test performance, available school resources, and unmet needs. The discussion begins with the concept of academic achievement and the ways it is measured. After that, we analyze the policies impacting academic achievement, most notably the No Child Left Behind (NCLB) Act. Next, we suggest the strategies to improve academic performance in the Nevada K12 System and make recommendations to increase parental involvement in education and encourage culturally competent policies of bringing together children, families, and schools. Finally, we discuss the resources needed to raise academic performances in Nevada schools

Animal waste management

"71/1M""Livestock producers have asked for guidelines on animal waste management that will be feasible and enduring. The Missouri Water Pollution Board has been aware of the need for improvements in methods of handling waste from confined feeding operations and for guidelines for producers. Chapter 204 of Missouri Statutes, as amended, gives the Water Pollution Board the responsibility and authority to correct and/or prevent "pollution" of "waters of the state." These terms are defined in the law and discussed briefly in the first section. With these facts in mind, staff engineers of the Water Pollution Board held a series of meetings with staff members of the Extension Division and Department of Agricultural Engineering of the University of Missouri-Columbia to develop guidelines for disposing of waste from confinement feeding operations. This report is a result of their combined efforts. Others assisting with various phases of development of these guidelines included: School of Engineering, University of Missouri-Columbia; State Department of Health, and the Soil Conservation Service. Research data and experience in handling livestock wastes have been used to develop the guidelines for planning, design, construction, and management of alternative systems of livestock waste management. The information and design guidelines herein are intended primarily for the use of personnel in agencies concerned with animal waste management problems." --PrefaceMissouri Water Pollution Board and Extension Division, University of Missouri - Columbia

How uncertainty enables non-classical dynamics

The uncertainty principle limits quantum states such that when one observable takes predictable values there must be some other mutually unbiased observables which take uniformly random values. We show that this restrictive condition plays a positive role as the enabler of non-classical dynamics in an interferometer. First we note that instantaneous action at a distance between different paths of an interferometer should not be possible. We show that for general probabilistic theories this heavily curtails the non-classical dynamics. We prove that there is a trade-off with the uncertainty principle, that allows theories to evade this restriction. On one extreme, non-classical theories with maximal certainty have their non-classical dynamics absolutely restricted to only the identity operation. On the other extreme, quantum theory minimises certainty in return for maximal non-classical dynamics.Comment: 4 pages + 4 page technical supplement, 2 figure