Isostaticity and the solidification of semiflexible polymer melts

Using molecular dynamics simulations of a tangent-soft-sphere bead-spring polymer model, we examine the degree to which semiflexible polymer melts solidify at isostaticity. Flexible and stiff chains crystallize when they are isostatic as defined by appropriate degree-of-freedom-counting arguments. Semiflexible chains also solidify when isostatic if a generalized isostaticity criterion that accounts for the slow freezing out of configurational freedom as chain stiffness increases is employed. The dependence of the average coordination number at solidification $Z(T_s)$ on chains' characteristic ratio $C_\infty$ has the same functional form [$Z \simeq a - b\ln(C_\infty)$] as the dependence of the average coordination number at jamming $Z(\phi_J)$ on $C_\infty$ in athermal systems, suggesting that jamming-related phenomena play a significant role in thermal polymer solidification

SYSTEMS ANALYSIS OF LIVESTOCK WASTE MANAGEMENT: A STUDY OF LARGE-SCALE DAIRYING

The analytical approach to studying waste management is investigated here in the context of large scale dairying. The typical short-run approach that regards waste management as separable from primary production is contrasted with a longer-run systems approach in which waste management is regarded as an interdependent stage of production. Failure to consider interdependencies between waste management and agricultural production could compromise potential efficiencies in the overall system. Furthermore, cooperative waste treatment and disposal among livestock producers may contribute to greater efficiency and afford opportunities for resource conservation and recovery through waste utilization.Environmental Economics and Policy, Livestock Production/Industries,

Strain Hardening in Polymer Glasses: Limitations of Network Models

Simulations are used to examine the microscopic origins of strain hardening in polymer glasses. While traditional entropic network models can be fit to the total stress, their underlying assumptions are inconsistent with simulation results. There is a substantial energetic contribution to the stress that rises rapidly as segments between entanglements are pulled taut. The thermal component of stress is less sensitive to entanglements, mostly irreversible, and directly related to the rate of local plastic arrangements. Entangled and unentangled chains show the same strain hardening when plotted against the microscopic chain orientation rather than the macroscopic strain.Comment: 4 pages, 3 figure

Ecological Studies of Wolves on Isle Royale

Annual Report 2022-2023https://digitalcommons.mtu.edu/wolf-annualreports/1064/thumbnail.jp

Ecological Studies of Wolves on Isle Royale Annual Report 2020-2021

Annual Report 2020-2021https://digitalcommons.mtu.edu/wolf-annualreports/1000/thumbnail.jp

Ecological Studies of Wolves on Isle Royale, 2018-2019

Annual Report 2018-2019https://digitalcommons.mtu.edu/wolf-annualreports/1002/thumbnail.jp

Ecological Studies of Wolves on Isle Royale Annual Report 2021-2022

Annual Report 2021-2022https://digitalcommons.mtu.edu/wolf-annualreports/1063/thumbnail.jp

Ecological Studies of Wolves on Isle Royale, 2019-2020

Annual Report 2019-2020https://digitalcommons.mtu.edu/wolf-annualreports/1001/thumbnail.jp

Ecological Studies of Wolves on Isle Royale, 2017-2018

Annual Report 2017-2018https://digitalcommons.mtu.edu/wolf-annualreports/1003/thumbnail.jp

Seismic signals are crucial for male mating success in a visual specialist jumping spider (Araneae: Salticidae)

The diversity of courtship displays throughout the animal kingdom is immense and displays can range from seemingly simple, to incredibly complex. Signalers often possess elaborate morphological adaptations for signals directed at a specific sensory modality in receivers. In some cases, these signals are so compelling to human observers, the possibility that important signals exist in other sensory modalities is ignored, potentially resulting in an incomplete characterization of the communication system. Jumping spiders (Salticidae) have remarkable visual capabilities. Yet one species, Habronattus dossenus, has recently been shown to have a complex repertoire of multicomponent seismic courtship signals in addition to and produced in concert with its multiple visual ornaments and movement displays. Here, we demonstrate the importance of these seismic signals in the courtship display of H. dossenus by comparing mating frequencies across experimentally manipulated treatments. Virgin females were paired with males from one of two experimental groups: nonmuted males or muted males. We found that females were significantly more likely to copulate with nonmuted males than with muted males. Furthermore, in all pairs that copulated, the latency to copulation was significantly shorter in nonmuted pairings than in muted pairings and precopulatory cannibalism rates were significantly lower. These results demonstrate that seismic signals are a critical component of male H. dossenus courtship displays. Additionally, we demonstrate that many other Habronattus species include a diversity of seismic signals in their courtship displays and we discuss potential selection pressures that may drive the evolution of multimodal displays even in species that already possess elaborate morphological adaptations for signals directed at one sensory modality