Adjustment of posture as a measure to accommodate uneven ground

In this work, we gained more insight into the functional role of trunk in human locomotion through the exploration of the biomechanical behavior of human walking in the presence of an expected twofold perturbation. First, this work presents the influence of the trunk orientation on leg function with stress on the analogy between locomotion in birds and humans (Chapter 2). By examining the human leg function during walking under changes in the trunk kinematics — up to the maximal sagittal flexion — and comparing it to that of small-bodied birds, we found that mimicking the birds’ posture induces a comparable behavior in leg function despite a different body size and morphology of the segmented legs. Furthermore, comparison of two simplified models for the first time, namely spring and damper in series and parallel spring and damper, revealed that the former model predicts the axial leg forces superior than the latter model during stance phase of walking with various degrees of trunk orientation

A multifactorial approach to improving captive primate welfare and enclosure usage

This thesis examines factors affecting the welfare of captive primates from a multi- factorial perspective: positional and non-positional behaviour, anatomical adaptations and enclosure usage. Past studies have shown that the provision of naturalistic environments for primates reduces stereotypical behaviours, decreases inactivity (Honess and Marin 2005; Zaragoza et al. 2011), and encourages species- typical positional behaviour repertoires (Jensvold et al. 2001). This suggests that encouraging species-typical behaviour improves captive primate welfare. It was found that reduced occurrence of stereotypical behaviour was associated with enrichment encouraging tool-use, a high fibre diet, and increased social behaviour. Compared to wild gorillas, captive gorillas adopted similar feeding and resting postures but performed substantially less vertical climbing, likely arising from differences in habitat structure and food distribution. It was found that the genus Gorilla has a strong preference for <20cm diameter and vertical/angled supports, but equally, gorillas have to some extent retained locomotor plasticity as suggested by Myatt et al. (2011) and Neufuss et al. (2014). Thus, from construction of a 3D musculoskeletal model of a hindlimb, it was found that bipedalism was associated with higher moment arms and torque around the hip, knee and ankle (except for extensor torque), than vertical climbing. This indicates that in terms of moment arms and torque, the ability to walk bipedally is not restricted by musculoskeletal adaptations to vertical climbing. It was also found that the gorilla foot had interossei that attached to distal phalanges, which may be important for fine flexion movements for grasping/manipulation of objects. These findings stress the importance of taking into account locomotor restrictions and plasticity when encouraging species-typical behaviour, which has not previously been emphasized. Further, accurate quantification of support availability and preference for enclosure design and positional behaviour studies has not been achieved before. Thus a novel method of studying enclosure usage was developed, via construction and analysis of a computer-aided design model of an enclosure. Besides successful accurate quantification of support preference and availability, the model permitted identification of specific favoured supports/areas and behaviour trends

Metastable legged-robot locomotion

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2008.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Includes bibliographical references (p. 195-215).A variety of impressive approaches to legged locomotion exist; however, the science of legged robotics is still far from demonstrating a solution which performs with a level of flexibility, reliability and careful foot placement that would enable practical locomotion on the variety of rough and intermittent terrain humans negotiate with ease on a regular basis. In this thesis, we strive toward this particular goal by developing a methodology for designing control algorithms for moving a legged robot across such terrain in a qualitatively satisfying manner, without falling down very often. We feel the definition of a meaningful metric for legged locomotion is a useful goal in and of itself. Specifically, the mean first-passage time (MFPT), also called the mean time to failure (MTTF), is an intuitively practical cost function to optimize for a legged robot, and we present the reader with a systematic, mathematical process for obtaining estimates of this MFPT metric. Of particular significance, our models of walking on stochastically rough terrain generally result in dynamics with a fast mixing time, where initial conditions are largely "forgotten" within 1 to 3 steps. Additionally, we can often find a near-optimal solution for motion planning using only a short time-horizon look-ahead. Although we openly recognize that there are important classes of optimization problems for which long-term planning is required to avoid "running into a dead end" (or off of a cliff!), we demonstrate that many classes of rough terrain can in fact be successfully negotiated with a surprisingly high level of long-term reliability by selecting the short-sighted motion with the greatest probability of success. The methods used throughout have direct relevance to machine learning, providing a physics-based approach to reduce state space dimensionality and mathematical tools to obtain a scalar metric quantifying performance of the resulting reduced-order system.by Katie Byl.Ph.D

Socioecology of Cat Ba Langurs (Trachypithecus poliocephalus): Implications for Conservation

Cat Ba langurs (Trachypithecus poliocephalus), endemic to Cat Ba Island (Vietnam), are a member of the limestone langur group (francoisi species-group) found in Laos, Vietnam, and China. With less than 75 individuals in the world, these Cat Ba langurs are Critically Endangered. This dissertation represents the first long-term behavioural study of the species (549 contact hours across 11 months), and provides socioecological information for two groups (n=17-20) living on the Cua Dong fjord, which can be used in conservation management. Like most other colobines, the majority of the Cat Ba langur diet is leaves (84% of their dietary budget). This may explain their activity budget, which is primarily inactivity (55% of their activity budget), followed by foraging (19%) and social behaviour and locomotion (12% each). Activity and dietary budgets vary seasonally, with animals spending more time in social behaviours in the wet season, when they eat more fruit, and more time in foraging in the dry season, when leaves are ingested more, suggesting they are energy maximisers. In addition, age differences were found, with adults spending the most time in social behaviours and resting. Social behaviour primarily includes grooming and playing with others - play is more common in younger animals, while older animals tend to groom more. Overall, they spend 58% of their days not in proximity to any other langurs. Adult males spend the most time alone, and seem to avoid young langurs. Disputes tend to be between adult females, and two females only tend to come together if there is a young langur acting as a ‘social glue’. Home ranges varied between groups with the larger group’s range being 50ha compared to just 22ha for the smaller group. In both areas, rocks and sparsely covered areas are used most often, which is due to the shrubby, discontinuous vegetation. Most of the langurs’ observable time is spent on exposed slopes (47%), followed by steep cliffs (38%), summits (11%), valleys (3%), and the ground (1%); this varied seasonally, likely to balance foraging needs with thermoregulation. The langurs used 22 sleeping sites, including ledges (61%) and caves (17%). When newborn, Cat Ba langurs are bright orange. They start to lose this natal coat as an infant, and become much darker during the young juvenile stage. As individuals age, they also become more independent and start to forage and locomote more on their own. These reported behaviours can be used to create a baseline for activity budgets, home range size, and habitat use, and development and maturation that can be used for comparative purposes in future studies. Results find that animals are behaviourally similar to other related species and their biggest threat is likely their small, fragmented population structure. To combat this, I support habitat protection, patrols, and enforcement; education and training; habitat corridors; and limiting the human population, as these support an entire ecosystem while teaching locals the importance of biodiversity, reducing resource competition, and fragmentation from infrastructure, and providing a means for the langurs themselves to disperse

Laterality and Babble: Does asymmetry in lip opening during babble indicate increasing left hemisphere dominance as babies gain articulatory experience?

Speech and language are supported by task-dependent neural networks that are predominantly lateralised to the left hemisphere of the brain, whilst emotion is supported by predominantly right hemispheric networks. This is reflected in the asymmetry of lip openings during speech and facial expressions in adults. One cross-sectional orofacial asymmetry study found an analogous distinction between 5-12-month-old babies’ lip openings during reduplicated babble and during positively valenced emotional facial expressions and this has been interpreted as evidence to support the hypothesis that babble is fundamentally linguistic in nature (Holowka & Petitto, 2002). However, a similar distinction is also observed in orofacial behaviours in some non-human primates. Differential hemispheric specialisation for emotional and vocal communicative functions may then be an ancient trait, long predating human language. Additionally, characterising babble as babies’ immature attempts to do language marginalises the critical role of endogenously motivated vocal exploration and may assume a degree of goal-directedness in infant behaviour around the time of babble emergence for which we have little other supporting evidence. This thesis explores laterality in eight 5-12-month-old’s babble, positive facial expressions, and other vocalisations longitudinally. Singleton and variegated babble are captured as well as reduplicated babble, and an alternative method for analysing orofacial asymmetry – hemimouth measurement – is used. Overall, Holowka and Petitto’s between-category distinction was replicated. However, babble was found to show right laterality at emergence and become left lateralised gradually over developmental time. Some interactional effect of utterance complexity was also observed. Bisyllabic babbles showed significant leftward shift over developmental time, whilst monosyllabic and polysyllabic babbles did not. Furthermore, hemimouth measurement revealed a degree of real-time variability in the laterality of babble not previously observed. An alternative theory of the underlying nature of babble – the Old Parts, New Machine hypothesis – is proposed

Neuroimaging of human motor control in real world scenarios: from lab to urban environment

The main goal of this research programme was to explore the neurophysiological correlates of human motor control in real-world scenarios and define mechanism-specific markers that could eventually be employed as targets of novel neurorehabilitation practice. As a result of recent developments in mobile technologies it is now possible to observe subjects' behaviour and monitor neurophysiological activity whilst they perform natural activities freely. Investigations in real-world scenarios would shed new light on mechanisms of human motor control previously not observed in laboratory settings and how they could be exploited to improve rehabilitative interventions for the neurologically impaired. This research programme was focussed on identifying cortical mechanisms involved in both upper- (i.e. reaching) and lower-limb (i.e. locomotion) motor control. Complementary results were obtained by the simultaneous recordings of kinematic, electromyographic and electrocorticographic signals. To study motor control of the upper-limb, a lab­based setup was developed, and the reaching movement of healthy young individuals was observed in both stable and unstable (i.e. external perturbation) situations. Robot-mediated force-field adaptation has the potential to be employed in rehabilitation practice to promote new skills learning and motor recovery. The muscular (i.e. intermuscular couplings) and neural (i.e. spontaneous oscillations and cortico­muscular couplings) indicators of the undergoing adaptation process were all symbolic of adaptive strategies employed during early stages of adaptation. The medial frontal, premotor and supplementary motor regions appeared to be the principal cortical regions promoting adaptive control and force modulation. To study locomotion control, a mobile setup was developed and daily life human activities (i.e. walking while conversing, walking while texting with a smartphone) were investigated outside the lab. Walking in hazardous environments or when simultaneously performing a secondary task has been demonstrated to be challenging for the neurologically impaired. Healthy young adults showed a reduced motor performance when walking in multitasking conditions, during which whole-brain and task-specific neural correlates were observed. Interestingly, the activity of the left posterior parietal cortex was predictive of the level of gait stability across individuals, suggesting a crucial role of this area in gait control and determination of subject specific motor capabilities. In summary, this research programme provided evidence on different cortical mechanisms operative during two specific scenarios for "real­world" motor behaviour in and outside the laboratory-setting in healthy subjects. The results suggested that identification of neuro-muscular indicators of specific motor control mechanisms could be exploited in future "real-world" rehabilitative practice

Using MapReduce Streaming for Distributed Life Simulation on the Cloud

Distributed software simulations are indispensable in the study of large-scale life models but often require the use of technically complex lower-level distributed computing frameworks, such as MPI. We propose to overcome the complexity challenge by applying the emerging MapReduce (MR) model to distributed life simulations and by running such simulations on the cloud. Technically, we design optimized MR streaming algorithms for discrete and continuous versions of Conway’s life according to a general MR streaming pattern. We chose life because it is simple enough as a testbed for MR’s applicability to a-life simulations and general enough to make our results applicable to various lattice-based a-life models. We implement and empirically evaluate our algorithms’ performance on Amazon’s Elastic MR cloud. Our experiments demonstrate that a single MR optimization technique called strip partitioning can reduce the execution time of continuous life simulations by 64%. To the best of our knowledge, we are the first to propose and evaluate MR streaming algorithms for lattice-based simulations. Our algorithms can serve as prototypes in the development of novel MR simulation algorithms for large-scale lattice-based a-life models.https://digitalcommons.chapman.edu/scs_books/1014/thumbnail.jp