A Study of the S=1/2 Alternating Chain using Multiprecision Methods

In this paper we present results for the ground state and low-lying excitations of the $S=1/2$ alternating Heisenberg antiferromagnetic chain. Our more conventional techniques include perturbation theory about the dimer limit and numerical diagonalization of systems of up to 28 spins. A novel application of multiple precision numerical diagonalization allows us to determine analytical perturbation series to high order; the results found using this approach include ninth-order perturbation series for the ground state energy and one magnon gap, which were previously known only to third order. We also give the fifth-order dispersion relation and third-order exclusive neutron scattering structure factor for one-magnon modes and numerical and analytical binding energies of S=0 and S=1 two-magnon bound states.Comment: 16 pages, 9 figures. for submission to Phys.Rev.B. PICT files of figs available at http://csep2.phy.ornl.gov/theory_group/people/barnes/barnes.htm

Failures in transport infrastructure embankments

To ensure that road and rail transport networks remain operational, both highway and railway embankments require continual maintenance and renewal to mitigate against ongoing deterioration and repair any sections damaged by realised failures. This paper provides a review of recent developments in the understanding of highway and railway embankment degradation and failure. Failures due to pore water pressure increase, seasonal shrink-swell deformation and progressive failure are considered. The material composition and construction of highway and railway embankments differ, which influences the dominant type and timing of embankment failure. There is evidence for highway embankment failures induced by pore water pressure increase, but not seasonal deformation and progressive failure. Some railway embankments are susceptible to pore water pressure increase, seasonal shrink-swell deformation and progressive failure due to the age and nature of the dumped clay fill used in their construction. The approaches used to measure and explore embankment failure mechanisms are compared and discussed. Field observations have been used to understand pore water pressure increase and seasonal shrink-swell deformation in embankments, while the investigation of progressive embankment failure has mainly utilised physical and numerical modelling approaches. Further field and laboratory investigation is required before the rigorous analysis of embankment failure can be routinely undertaken. However, progress is being made to empirically identify and evaluate the various risk factors affecting transport infrastructure embankment failure

A sublime opportunity: The dynamics of transitioning cometary bodies and the feasibility of in situ observations of the evolution of their activity

The compositional and morphological evolution of minor bodies in the solar system is primarily driven by the evolution of their heliocentric distances, as the level of incident solar radiation regulates cometary activity. We investigate the dynamical transfer of Centaurs into the inner solar system, facilitated by mean motion resonances with Jupiter and Saturn. The recently discovered object P/2019 LD2 will transition from the Centaur region to the inner solar system in 2063. In order to contextualize LD2, we perform N-body simulations of a population of Centaurs and Jupiter-family comets. Objects between Jupiter and Saturn with Tisserand parameter TJ ∼ 3 are transferred onto orbits with perihelia q < 4 au within the next 1000 yr with notably high efficiency. Our simulations show that there may be additional LD2-like objects transitioning into the inner solar system in the near future, all of which have low δV with respect to Jupiter. We calculate the distribution of orbital elements resulting from a single Jovian encounter and show that objects with initial perihelia close to Jupiter are efficiently scattered to q < 4 au. Moreover, approximately 55% of the transitioning objects in our simulated population experience at least one Jovian encounter prior to reaching q < 4 au. We demonstrate that a spacecraft stationed near Jupiter would be well positioned to rendezvous, orbit-match, and accompany LD2 into the inner solar system, providing an opportunity to observe the onset of intense activity in a pristine comet in situ. Finally, we discuss the prospect of identifying additional targets for similar measurements with forthcoming observational facilities. © Investigaciones Historicas 2021.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Analysis of neuropsychiatric disease-related functional neuroanatomical markers in mice.

A better alignment of preclinical and clinical neurobiological measures could help improve neuropsychiatric disease therapeutic development. This unit describes a compendium of hypothesis-driven neuroanatomical phenotyping strategies to be employed in genetic mouse models. Using neuropsychiatric disease-based alterations as a guide, these are histological and immunohistochemical methodologies also applied to human tissue. They include quantification assays of neurochemical-, newly born neuron- and glial-cell markers, synaptic proteins, regional volumetrics, dendritic complexity and spine number as well as an index of excitation/inhibition balance. The techniques can be implemented in isolation or to complement concordant behavioral and electrophysiological analyses. Each outcome will provide functional detail necessary to decipher underlying neural circuit abnormalities associated with a brain-related phenotype in mice. Experimental design, timing, anticipated results and potential pitfalls are discussed. © 2018 by John Wiley &amp; Sons, Inc

Adaptability and Reliability of Yield for Four Bell Pepper Cultivars Across Three Southeastern States

(Capsicum annuum L.) cultivars were evaluated for yield (total weight of marketable fruit) performance over 41 environments as combinations of 3 years, three planting dates, and seven locations across North Carolina, South Carolina, and Georgia. Cultural practices, including trickle irrigation and double rows planted on blackplastic- covered beds, were uniform across all environments, except for fertilization, which was adjusted at each location based on soil tests. Comparing production over 3 years between the mountain location and the Coastal Plain location in North Carolina, yields were lower on the Coastal Plain. Spring plantings provided higher yields than summer plantings at both locations. Yield increases were obtained from hybrid cultivars over that of the open-pollinated (OP) standard [‘Keystone Resistant Giant #3’ (KRG#3)] in the summer planting in the mountains compared to the Tidewater Coastal Plain. Across the three-state region, hybrid cultivar yields were higher than those of the OP cultivar for the second spring planting date in 1986 and 1987. Although the hybrid yields were higher than that of the OP standard, the hybrid ‘Skipper’ yielded less than the other hybrids (‘Gator Belle’ and ‘Hybelle’). ‘Gator Belle’ generally out-yielded ‘Hybelle’ at all locations, except in Fletcher, N.C. This difference may be related to the relative sensitivity of these two cultivars to temperature extremes, rather than soil or geographic factors, because there was a tendency for ‘Hybelle’ yields to exceed ‘Gator Belle’ in the earliest planting date. Based on the reliability index, the chance of outperforming KRG#3 (the standard) was 85% for ‘Hybelle’, 80% for ‘Gator Belle’, but only 67% for ‘Skipper’