A Note on Encodings of Phylogenetic Networks of Bounded Level

Driven by the need for better models that allow one to shed light into the question how life's diversity has evolved, phylogenetic networks have now joined phylogenetic trees in the center of phylogenetics research. Like phylogenetic trees, such networks canonically induce collections of phylogenetic trees, clusters, and triplets, respectively. Thus it is not surprising that many network approaches aim to reconstruct a phylogenetic network from such collections. Related to the well-studied perfect phylogeny problem, the following question is of fundamental importance in this context: When does one of the above collections encode (i.e. uniquely describe) the network that induces it? In this note, we present a complete answer to this question for the special case of a level-1 (phylogenetic) network by characterizing those level-1 networks for which an encoding in terms of one (or equivalently all) of the above collections exists. Given that this type of network forms the first layer of the rich hierarchy of level-k networks, k a non-negative integer, it is natural to wonder whether our arguments could be extended to members of that hierarchy for higher values for k. By giving examples, we show that this is not the case

Frequency of Aspirating Gastric Tubes for Patients Receiving Enteral Nutrition in the ICU: A Randomised Controlled Trial

Background: Enteral nutrition (EN) tolerance is often monitored by aspirating stomach contents by syringe at prescribed intervals. No studies have been conducted to assess the most appropriate time interval for aspirating gastric tubes. We compared gastric tube aspirations every 4 hours (usual care) with a variable regimen (up to every 8 hours aspirations).Methods: This randomized controlled trial (RCT) enrolled patients who stayed in the intensive care unit (ICU) for >48 hours, had a gastric tube, and were likely to receive EN for 3 or more days. Patients were randomized (computer-generated randomization) to either the control (every 4 hours) or intervention group (variable regimen). The primary outcome was number of gastric tube aspirations per day from randomization until EN was ceased or up to 2 weeks postrandomization.Results: Following Institutional Ethics Committee approval, 357 patients were recruited (control group, n = 179; intervention group, n = 178). No differences were found in age, sex, worst APACHE II score, or time to start of EN. In the intention-to-treat analysis, the intervention group had fewer tube aspirations per day (3.4 versus 5.4 in the control group, P < .001). Vomiting/regurgitation was increased in the intervention group (2.1% versus 3.6%, P = .02). There were no other differences in complications.Conclusion: This is the first RCT to examine the frequency of gastric tube aspirations. The frequency of gastric tube aspirations was reduced in the variable-regimen group with no increase in risk to the patient. Reducing the frequency of aspirations saves nursing time, decreases risk of contamination of feeding circuit, and minimizes risk of body fluid exposure

Early development of spasticity following stroke: a prospective, observational trial

This study followed a cohort of 103 patients at median 6 days, 6 and 16 weeks after stroke and recorded muscle tone, pain, paresis, Barthel Index and quality of life score (EQ-5D) to identify risk-factors for development of spasticity. 24.5% of stroke victims developed an increase of muscle tone within 2 weeks after stroke. Patients with spasticity had significantly higher incidences of pain and nursing home placement and lower Barthel and EQ-5D scores than patients with normal muscle tone. Early predictive factors for presence of severe spasticity [modified Ashworth scale score (MAS) ≥3] at final follow-up were moderate increase in muscle tone at baseline and/or first follow-up (MAS = 2), low Barthel Index at baseline, hemispasticity, involvement of more than two joints at first follow-up, and paresis at any assessment point. The study helps to identify patients at highest risk for permanent and severe spasticity, and advocates for early treatment in this group

Nonlinear Supersymmetry as a Hidden Symmetry

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Muscle weakness and lack of reflex gain adaptation predominate during post-stroke posture control of the wrist

Instead of hyper-reflexia as sole paradigm, post-stroke movement disorders are currently considered the result of a complex interplay between neuronal and muscular properties, modified by level of activity. We used a closed loop system identification technique to quantify individual contributors to wrist joint stiffness during an active posture task. Continuous random torque perturbations applied to the wrist joint by a haptic manipulator had to be resisted maximally. Reflex provoking conditions were applied i.e. additional viscous loads and reduced perturbation signal bandwidth. Linear system identification and neuromuscular modeling were used to separate joint stiffness into the intrinsic resistance of the muscles including co-contraction and the reflex mediated contribution. Compared to an age and sex matched control group, patients showed an overall 50% drop in intrinsic elasticity while their reflexive contribution did not respond to provoking conditions. Patients showed an increased mechanical stability compared to control subjects. Post stroke, we found active posture tasking to be dominated by: 1) muscle weakness and 2) lack of reflex adaptation. This adds to existing doubts on reflex blocking therapy as the sole paradigm to improve active task performance and draws attention to muscle strength and power recovery and the role of the inability to modulate reflexes in post stroke movement disorders.Mechanical, Maritime and Materials Engineerin

Upper limb impairments associated with spasticity in neurological disorders

<p>Abstract</p> <p>Background</p> <p>While upper-extremity movement in individuals with neurological disorders such as stroke and spinal cord injury (SCI) has been studied for many years, the effects of spasticity on arm movement have been poorly quantified. The present study is designed to characterize the nature of impaired arm movements associated with spasticity in these two clinical populations. By comparing impaired voluntary movements between these two groups, we will gain a greater understanding of the effects of the type of spasticity on these movements and, potentially a better understanding of the underlying impairment mechanisms.</p> <p>Methods</p> <p>We characterized the kinematics and kinetics of rapid arm movement in SCI and neurologically intact subjects and in both the paretic and non-paretic limbs in stroke subjects. The kinematics of rapid elbow extension over the entire range of motion were quantified by measuring movement trajectory and its derivatives; i.e. movement velocity and acceleration. The kinetics were quantified by measuring maximum isometric voluntary contractions of elbow flexors and extensors. The movement smoothness was estimated using two different computational techniques.</p> <p>Results</p> <p>Most kinematic and kinetic and movement smoothness parameters changed significantly in paretic as compared to normal arms in stroke subjects (p < 0.003). Surprisingly, there were no significant differences in these parameters between SCI and stroke subjects, except for the movement smoothness (p ≤ 0.02). Extension was significantly less smooth in the paretic compared to the non-paretic arm in the stroke group (p < 0.003), whereas it was within the normal range in the SCI group. There was also no significant difference in these parameters between the non-paretic arm in stroke subjects and the normal arm in healthy subjects.</p> <p>Conclusion</p> <p>The findings suggest that although the cause and location of injury are different in spastic stroke and SCI subjects, the impairments in arm voluntary movement were similar in the two spastic groups. Our results also suggest that the non-paretic arm in stroke subjects was not distinguishable from the normal, and might therefore be used as an appropriate control for studying movement of the paretic arm.</p

Tizanidine does not affect the linear relation of stretch duration to the long latency M2 response of m. flexor carpi radialis

The long latency M2 electromyographic response of a suddenly stretched active muscle is stretch duration dependent of which the nature is unclear. We investigated the influence of the group II afferent blocker tizanidine on M2 response characteristics of the m. flexor carpi radialis (FCR). M2 response magnitude and eliciting probability in a group of subjects receiving 4 mg of tizanidine orally were found to be significantly depressed by tizanidine while tizanidine did not affect the significant linear relation of the M2 response to stretch duration. The effect of tizanidine on the M2 response of FCR is supportive of a group II afferent contribution to a compound response of which the stretch duration dependency originates from a different mechanism, e.g., rebound Ia firing

Functional Connectivity in Tactile Object Discrimination—A Principal Component Analysis of an Event Related fMRI-Study

BACKGROUND: Tactile object discrimination is an essential human skill that relies on functional connectivity between the neural substrates of motor, somatosensory and supramodal areas. From a theoretical point of view, such distributed networks elude categorical analysis because subtraction methods are univariate. Thus, the aim of this study was to identify the neural networks involved in somatosensory object discrimination using a voxel-based principal component analysis (PCA) of event-related functional magnetic resonance images. METHODOLOGY/PRINCIPAL FINDINGS: Seven healthy, right-handed subjects aged between 22 and 44 years were required to discriminate with their dominant hand the length differences between otherwise identical parallelepipeds in a two-alternative forced-choice paradigm. Of the 34 principal components retained for analysis according to the 'bootstrapped' Kaiser-Guttman criterion, t-tests applied to the subject-condition expression coefficients showed significant mean differences between the object presentation and inter-stimulus phases in PC 1, 3, 26 and 32. Specifically, PC 1 reflected object exploration or manipulation, PC 3 somatosensory and short-term memory processes. PC 26 evinced the perception that certain parallelepipeds could not be distinguished, while PC 32 emerged in those choices when they could be. Among the cerebral regions evident in the PCs are the left posterior parietal lobe and premotor cortex in PC 1, the left superior parietal lobule (SPL) and the right cuneus in PC 3, the medial frontal and orbitofrontal cortex bilaterally in PC 26, and the right intraparietal sulcus, anterior SPL and dorsolateral prefrontal cortex in PC 32. CONCLUSIONS/SIGNIFICANCE: The analysis provides evidence for the concerted action of large-scale cortico-subcortical networks mediating tactile object discrimination. Parallel to activity in nodes processing object-related impulses we found activity in key cerebral regions responsible for subjective assessment and validation

Maroon Archaeology Beyond the Americas: A View From Kenya

Archaeological research on Maroons—that is, runaway slaves—has been largely confined to the Americas. This essay advocates a more global approach. It specifically uses two runaway slave communities in 19th-century coastal Kenya to rethink prominent interpretive themes in the field, including “Africanisms,” Maroons’ connections to indigenous groups, and Maroon group cohesion and identity. This article’s analysis demonstrates that the comparisons enabled by a more globalized perspective benefit the field. Instead of eliding historical and cultural context, these comparisons support the development of more localized and historically specific understandings of individual runaway slave communities both in Kenya and throughout the New World