On Reconfiguring Tree Linkages: Trees can Lock

It has recently been shown that any simple (i.e. nonintersecting) polygonal chain in the plane can be reconfigured to lie on a straight line, and any simple polygon can be reconfigured to be convex. This result cannot be extended to tree linkages: we show that there are trees with two simple configurations that are not connected by a motion that preserves simplicity throughout the motion. Indeed, we prove that an $N$-link tree can have $2^{\Omega(N)}$ equivalence classes of configurations.Comment: 16 pages, 6 figures Introduction reworked and references added, as the main open problem was recently close

In Vivo Imaging to Characterize Dynamic Tissue Responses after Neural Electrode Implantation

Implantable neural electrodes are promising technologies to restore motor, sensory, and cognitive function in many neural pathologies through brain-computer interfacing (BCI). Many BCI applications require electrode implantation within neural tissue to resolve and/or modulate the physiological activity of individual neurons via electrical recording and stimulation. This invasive implantation leads to acute and long-term deterioration of both the electrode device as well as the neurons surrounding the device. Ultimately, damage to the electrode and neural tissue results in electrode recording failure within the first years after implantation. Many strategies to improve BCI longevity focus on mitigating tissue damage through improving neuronal survival or reducing inflammatory activity around implants. Despite incremental improvements, electrode failure persists as an obstacle to wide-spread clinical deployment of BCIs. This can be partly attributed to an incomplete understanding of the biological correlates of recording performance. These correlates have largely been identified through post-mortem histological staining, which cannot capture dynamic changes in cellular physiology and morphology. In the following dissertation, we use longitudinal two-photon in vivo imaging to quantify how neurons, microglia, and meningeal immune cells are affected by an intracortical electrode during and after implantation in mouse cortex. We go beyond conventional histological techniques to show the time-course of neuronal injury and microglial recruitment after implantation. Neuronal injury occurs instantaneously, with prolonged, high calcium levels evident in neurons within 100 µm of implants. Microglial activation occurs within minutes of implantation and subsequent microglial encapsulation of electrodes can be modulated by bioactive surface coatings. Within the first day post-implant, there is high trafficking of peripheral immune cells through venules at the surface of the brain as well as along the electrode’s shank at the surface of the brain. Over the next month, calcium activity in neurons increases while the collagenous meningeal tissues at the surface of the brain thicken. We further show that meningeal thickening can have profound implications for devices implanted into non-human primates as well. In sum, these results define new potential therapeutic targets and windows that could improve the longevity of implantable neural electrodes

Fourth Annual Workshop on Space Operations Applications and Research (SOAR 90)

The proceedings of the SOAR workshop are presented. The technical areas included are as follows: Automation and Robotics; Environmental Interactions; Human Factors; Intelligent Systems; and Life Sciences. NASA and Air Force programmatic overviews and panel sessions were also held in each technical area

PROGRAM and PROCEEDINGS THE NEBRASKA ACADEMY OF SCIENCES: 139th Anniversary Year, One Hundred-Twenty-Ninth Annual Meeting, April 12, 2019, NEBRASKA WESLEYAN UNIVERSITY, LINCOLN, NEBRASKA

PROGRAM AT-A-GLANCE FRIDAY, APRIL 12, 2019 7:30 a.m. REGISTRATION OPENS - Lobby of Lecture Wing, Olin Hall 8:00 Aeronautics and Space Science, Session A – Acklie 109 Aeronautics and Space Science, Session B – Acklie 111 Collegiate Academy; Biology, Session B - Olin B Biological and Medical Sciences, Session A - Olin 112 Biological and Medical Sciences, Session B - Smith Callen Conference Center Chemistry and Physics; Chemistry - Olin A 8:00 “Teaching and Learning the Dynamics of Cellular Respiration Using Interactive Computer Simulations” Workshop – Olin 110 9:30 “Life After College: Building Your Resume for the Future” Workshop – Acklie 218 8:25 Collegiate Academy; Chemistry and Physics, Session A – Acklie 007 8:36 Collegiate Academy; Biology, Session A - Olin 111 9:00 Chemistry and Physics; Physics – Acklie 320 9:10 Aeronautics and Space Science, Poster Session – Acklie 109 & 111 10:30 Aeronautics and Space Science, Poster Session – Acklie 109 & 111 11:00 MAIBEN MEMORIAL LECTURE: Dr David Swanson - OLIN B Scholarship and Friend of Science Award announcements 12:00 p.m. LUNCH – WESLEYAN CAFETERIA Round-Table Discussion – “Assessing the Academy: Current Issues and Avenues for Growth” led by Todd Young – Sunflower Room 12:50 Anthropology – Acklie 109 1:00 Applied Science and Technology - Olin 111 Biological and Medical Sciences, Session C - Olin 112 Biological and Medical Sciences, Session D - Smith Callen Conference Center Chemistry and Physics; Chemistry - Olin A Collegiate Academy; Biology, Session B - Olin B Earth Science – Acklie 007 Environmental Sciences – Acklie 111 Teaching of Science and Math – Acklie 218 1:20 Chemistry and Physics; Physics – Acklie 320 4:30 BUSINESS MEETING - OLIN B NEBRASKA ASSOCIATION OF TEACHERS OF SCIENCE (NATS) The 2019 Fall Conference of the Nebraska Association of Teachers of Science (NATS) will be held at the Younes Conference Center, Kearney, NE, September 19-21, 2019. President: Betsy Barent, Norris Public Schools, Firth, NE President-Elect: Anya Covarrubias, Grand Island Public Schools, Grand Island, NE AFFILIATED SOCIETIES OF THE NEBRASKA ACADEMY OF SCIENCES, INC. 1. American Association of Physics Teachers, Nebraska Section Web site: http://www.aapt.org/sections/officers.cfm?section=Nebraska 2. Friends of Loren Eiseley Web site: http://www.eiseley.org/ 3. Lincoln Gem & Mineral Club Web site: http://www.lincolngemmineralclub.org/ 4. Nebraska Chapter, National Council for Geographic Education 5. Nebraska Geological Society Web site: http://www.nebraskageologicalsociety.org Sponsors of a $50 award to the outstanding student paper presented at the Nebraska Academy of Sciences Annual Meeting, Earth Science /Nebraska Chapter, Nat\u27l Council Sections 6. Nebraska Graduate Women in Science 7. Nebraska Junior Academy of Sciences Web site: http://www.nebraskajunioracademyofsciences.org/ 8. Nebraska Ornithologists’ Union Web site: http://www.noubirds.org/ 9. Nebraska Psychological Association http://www.nebpsych.org/ 10. Nebraska-Southeast South Dakota Section Mathematical Association of America Web site: http://sections.maa.org/nesesd/ 11. Nebraska Space Grant Consortium Web site: http://www.ne.spacegrant.org

ITAP: Clinical outcomes and implant design optimisation using numerical modelling

Redistribution of the flow of forces through the body, such as that after amputation and/or implantation of a skeletally anchored amputation prostheses, leads to bone remodelling. Periprosthetic bone resorption can destabilise skeletally anchored amputation prostheses. Therefore, implants that minimise bone resorption will achieve a more successful long term bone fixation. Bone remodelling outcome measures rely on implant design using mechanoregulatory bone remodelling theory. Mechanoregulation is implemented by functions that link a local mechanical stimulus to a local change in the structure or properties of bone material. This thesis uses the strain adaptive remodelling theory at the time of implantation with periprosthetic strain energy density as the outcome parameter. Clinical trial data was collected from a patient with a skeletally anchored amputation prostheses; The Intraosseous Transcutaneous Amputation Prosthesis (ITAP). The clinical trial ran from 2008 – 2019, the data was investigated for patterns between implant design and fixation success. This thesis reports trends in fixation success and bone change using a developed fixation success score. There was an ideal implant length to bone length ratio range and a straight, tapered stem with a flared bone collar growth shape were beneficial to fixation success. Conversely, one or more parameters associated with pressfit fixation were detrimental to fixation success. Results between the clinical and numerical data compared favourably; clinically, regions of periprosthetic bone growth were also observed by regions of high strain energy density in the finite element analysis and vice versa at the implant tip and osteotomy face. This thesis provides skeletally anchored amputation prostheses design guidelines that will minimise bone resorption when measured with strain energy density. Moreover, that future skeletally anchored amputation prostheses parameterised design can and should be used as a tool to assess bone fixation outcome in pre-clinical assessments

Cascade Lake: A Novel

Twenty-two-year-old Macy Oman narrates the book in retrospect from Cascade, Oregon, where she is visiting her mother. Macy\u27s father moved with her to Portland shortly after the accidental death of her brother, Nick, seven years before the narration begins. Macy\u27s mother stayed behind in Cascade. Thematically the work centers on the emotional repercussions of these losses. Macy\u27s, and her older lover Jason\u27s, involvement with Nick\u27s death is unknown to everyone. Her guilt and her mother\u27s perceived betrayal are disabling. Taking her longing for closeness to nature and to her reclusive friend Celia, Macy discovers folklore that inspires a vision quest to seek her own personal healer, a shaman inside. When Macy accepts and reveals her part in Nick\u27s death, it opens the way to further revelations about the real root of her parents\u27 separation, the divisive nature of assumptions, and the healing power of acceptance. This story attempts to loosely rewrite, subvert or reclaim the early life of the mythological Medea, who betrayed her father and her brother by aiding her lover, Jason the Argonaught, in his quest to obtain the golden fleece that hung on an oak tree, guarded by a dragon. In this story, the golden fleece is represented by an Apollo scarf that Macy\u27s father Richard, an eccentric art-history buff, bought for her mother. Mythologically, the fleece was a powerful artifact, heavily guarded, worthy of war. In this rendition, the value of the scarf, rather than being material, is emotional. In comparison with the golden fleece, the Apollo scarf, an expensive item that is only appreciated for the relationships it represents, is meant to signal the superiority of the emotional over the material. Ultimately Macy does not betray her family; it is Mari who stays behind and Macy who instigates a reconciliation when she reveals the truth about her somewhat inadvertent participation in Nick\u27s death. (352 pages

Separately, Connectedly: Exploring Trauma Through Ekphrasis in Contemporary Novels

This thesis examines ekphrasis as a rhetorical tool to explore, represent, and contemplate trauma affect in contemporary novels. From the Greek phrase for ‘description,’ ekphrasis is part of a long and ancient literary tradition, dating as far back as the ancient depictions of art on urns, weaponry, as well as more disambiguated descriptions of scenes and people. The uses of ekphrasis as a literary device are broad and complex, but its use is under-researched in contemporary novels, and there is a near total absence of investigation into ekphrasis within the novel as a means of contemplating and understanding the affect of a condition that is inherently abstract and disorienting.Literary trauma theory has evolved considerably in recent years. In keeping with important findings in psychology and psychiatric research, there is a broad recognition that rethinking trauma representation beyond the recitation and reliving of events and into textured descriptions of trauma affect is essential for thoughtful, nuanced explorations of an experience that resists narrative convenience. As a result, there are increased calls to accept and represent its inherent fractured nature and resist the authorial temptation to forge a story around it that fits neatly into a cohesive whole. This thesis proposes a framework for considering how various aspects of ekphrastic descriptions of real and imagined art as well as their connotative and denotative significance in the novel reveals nuance in the representation of trauma affect through the activation of language and image. The contemporary novels explored herein are: The Goldfinch by Donna Tartt, What I Loved by Siri Hustvedt, and How to Be Both by Ali Smith. Each of these novels present ekphrasis and affect differently, which enables broader testing of the flexibility of the proposed framework

Developing a System to Investigate Age-Related Differences in the Real-Time Utilization of Dynamically Changing External Cues during Navigation

Successful navigation depends critically upon two broad categories of sensory information, environmental (allothetic) and self-motion (idiothetic). Both the hippocampus and the medial portion of the entorhinal cortex (MEC) are critical for spatial navigation and contain functionally distinct sub-networks of spatially-modulated cells. These cells are characterized by their tuning to different spatial sensory-perceptual features of the environment and all utilize both allothetic and idiothetic cues to anchor and update their spatial firing to generate a comprehensive and dynamic representation of space. As with older adults, aged rats show pronounced impairments on a number of different spatial navigation tasks and these impairments are accompanied by a bias toward relying on egocentric over allocentric navigation strategies. Similarly, the hippocampus and MEC are also highly susceptible to age-associated changes. The influence visual allothetic cues exert on hippocampal place cell spatial tuning is diminished and delayed in aged animals. Two plausible and non-exclusive explanations that could account for these age-related alterations in allothetic processing are 1) circuit disruptions caused by known age-related functional and anatomical changes in the entorhinal-hippocampal processing pathway or 2) degraded sensory-perceptual information resulting from well-established age-related deficits across multiple sensory domains. Either of these possibilities could have the effect of either slowing allothetic cue processing or weakening the ability of these cues to influence firing field alignment. Within this context, this thesis was conceived with the aim of investigating the degree and timing with which young and aged animals utilize allothetic and idiothetic feedback to update their internal representation of space and calibrate their behavioral output. A large focus of this thesis is given to the incremental design and piloting of a number of novel technologies. Foremost among the methodological contributions of this study is the development of an augmented reality behavioral apparatus, termed the Instantaneous Cue Rotation (ICR) arena, which utilizes projected visual cues to allow for rapid remote control of all symmetry breaking visual features in the environment as rats actively engage in a visual-cue based goal navigation task. The results of extensive behavioral piloting of old and young rats validate both the ICR rotation manipulation as well as the mobile reward delivery system. This system traverses the track in tandem with the rat, enabling food based spatial reinforcement while preventing food-related olfactory cues from becoming associated with any specific location. In parallel with this work, microdrive technology was developed to enable simultaneous recording from both MEC and CA1 which is discussed along with results from single-region hippocampal and MEC implanted rats assessed in the context of a cue rotation manipulation conceptually similar to the that of the ICR. Finally, the results of the behavioral study suggest that in young rats the cue rotation exerts reliable but incomplete control over running behavior. In aged rats, by comparison, the cues exert an overall less pronounced influence on running behavior, consistent with known age-related deficits in allothetic processing. When assessed on a lap-by-lap basis, it was found that the behavior of both young and aged rats became progressively more aligned with the cues over the first few laps following cue rotation. These findings suggest a progressive realignment of behavior from an egocentric to an allocentric reference frame which is reminiscent of the reported progressive realignment of place field firing in response to conflicting spatial feedback