Interfacing peripheral nerve with macro-sieve electrodes following spinal cord injury

Macro-sieve electrodes were implanted in the sciatic nerve of five adult male Lewis rats following spinal cord injury to assess the ability of the macro-sieve electrode to interface regenerated peripheral nerve fibers post-spinal cord injury. Each spinal cord injury was performed via right lateral hemisection of the cord at the T9–10 site. Five months post-implantation, the ability of the macro-sieve electrode to interface the regenerated nerve was assessed by stimulating through the macro-sieve electrode and recording both electromyography signals and evoked muscle force from distal musculature. Electromyography measurements were recorded from the tibialis anterior and gastrocnemius muscles, while evoked muscle force measurements were recorded from the tibialis anterior, extensor digitorum longus, and gastrocnemius muscles. The macro-sieve electrode and regenerated sciatic nerve were then explanted for histological evaluation. Successful sciatic nerve regeneration across the macro-sieve electrode interface following spinal cord injury was seen in all five animals. Recorded electromyography signals and muscle force recordings obtained through macro-sieve electrode stimulation confirm the ability of the macro-sieve electrode to successfully recruit distal musculature in this injury model. Taken together, these results demonstrate the macro-sieve electrode as a viable interface for peripheral nerve stimulation in the context of spinal cord injury

Medical ultrasonic tomographic system

An electro-mechanical scanning assembly was designed and fabricated for the purpose of generating an ultrasound tomogram. A low cost modality was demonstrated in which analog instrumentation methods formed a tomogram on photographic film. Successful tomogram reconstructions were obtained on in vitro test objects by using the attenuation of the fist path ultrasound signal as it passed through the test object. The nearly half century tomographic methods of X-ray analysis were verified as being useful for ultrasound imaging

River Otter Distribution in Nebraska

The river otter (Lontra canadensis) was extirpated from Nebraska, USA, in the early 1900s and reintroduced starting in 1986. Information is needed regarding the distribution of river otters in Nebraska before decisions can be made regarding its conservation status. Understanding distribution of a species is critically important for effective management. We investigated river otter distribution in Nebraska with occupancy modeling and maximum entropy (Maxent) modeling using 190 otter sign observations on Nebraska’s navigable rivers and 380 historical otter records from November 1977 to April 2014. Both methods identified the Platte River, Elkhorn River, central and eastern Niobrara River, and southern Loup River system as core areas within the distribution of otters in Nebraska. The Maxent model provided more liberal estimates of site occupancy and identified some smaller rivers as being within the distribution of otters in Nebraska, which were not identified using occupancy modeling. We recommend that multiple data sets and analysis methods be used to estimate species distribution because this allows for the broadest geographical coverage and decreases the likelihood of overlooking areas with fewer animal records. If further reintroduction efforts or translocation efforts are to take place in the future, we recommend focusing on areas with high modeled occupancy but few historical and survey records

Scaling of unitary synaptic strength in the context of network dynamics

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Brain and Cognitive Sciences, 2005.Includes bibliographical references (leaves 93-97).A fundamental consideration in understanding neuronal networks is determining what sets the unitary functional strength of a synaptic connection between two cells, and what meta-processes such mechanisms answer to. This question can be asked either mechanistically, by characterizing the molecular processes that regulate the synapse's transmission, or ontologically, by considering the impact of this transmission from the standpoint of neighboring synapses, the post synaptic cell itself, or the network of neurons in which it is situated. The work presented here practices both approaches, by identifying a new molecular mechanism to which the quantal size of excitatory synapses can be attributed, and then beginning to explore how quantal size might be influenced by network activity and architecture. Chapter 1 identifies a new molecular control point for specifying the quantal size of excitatory transmission in the mammalian brain, and provides the first known demonstration that such specification can be provided by a presynaptic process. It then details how this mechanism is regulated by network activity.(cont.) Chapter 2 makes use of a new methodology for designing the physical structure of cultured networks in order to begin to perturb network parameters and explore the role of quantal size in a network context. Applying this methodology I demonstrate that the quantal size of excitatory synapses is scaled by neurons inversely with their number of synaptic connections, and identify a set of mechanisms by which network firing is maintained at a constant level when the number of active synaptic partners is scaled. Chapter 3 demonstrates progress towards a methodology capable of producing and detecting changes in the unitary strength of multiple synapses with respect to one another within a dendritic tree. Future efforts can hopefully make use of similar principles to directly visualize how heterosynaptic processes establish and maintain a contrast in the strengths of unitary synapses to enable representation by synaptically-based memory traces.by Nathan R. Wilson.Ph.D

Hooked on osprey – the role of an “iconic” wildlife species in outdoor education

Much of the narrative associated with wildlife and habitat conservation has focused on individual, often iconic species. In the United Kingdom one of the most significant wildlife re-introduction success stories has been that of osprey. Although present in several regions since the 1950s, it was not until 2001 that osprey nested in the Lake District National Park, Cumbria, England. The return of osprey, after an absence of 150 years, was a major opportunity to engage park visitors with new outdoor activities and education. To date, in excess of 1 million visitors have participated in osprey viewing at sites managed by the Lake District Osprey Project. A core feature of the project is an educational program involving the contribution of a team of 100 volunteers. Econometric analysis has demonstrated a net gain to the local economy from osprey eco-tourism of approximately £2M/year. However, there has not yet been a detailed analysis of visitor perceptions of the educational and social value of the osprey project. This presentation will share the results of a research study based at two osprey viewing sites in the Lake District National Park. Interviews were conducted with approximately 300 visitors and incorporated questions, which pertained to demographic information, lifestyle, well-being, attitudes to nature, as well as the learning experience from interacting with osprey project volunteers. Our findings highlight the role that species conservation can play in stimulating outdoor engagement and education, and as a catalyst for physical activity. We discuss some of the opportunities and challenges associated with sustainable wildlife projects, and identify several policy implications

Thermal modeling of subduction zones with prescribed and evolving 2D and 3D slab geometries

The determination of the temperature in and above the slab in subduction zones, using models where the top of the slab is precisely known, is important to test hypotheses regarding the causes of arc volcanism and intermediate-depth seismicity. While 2D and 3D models can predict the thermal structure with high precision for fixed slab geometries, a number of regions are characterized by relatively large geometrical changes. Examples include the flat slab segments in South America that evolved from more steeply dipping geometries to the present day flat slab geometry. We devise, implement, and test a numerical approach to model the thermal evolution of a subduction zone with prescribed changes in slab geometry over time. Our numerical model approximates the subduction zone geometry by employing time dependent deformation of a B\'ezier spline which is used as the slab interface in a finite element discretization of the Stokes and heat equations. We implement the numerical model using the FEniCS open source finite element suite and describe the means by which we compute approximations of the subduction zone velocity, temperature, and pressure fields. We compute and compare the 3D time evolving numerical model with its 2D analogy at cross-sections for slabs that evolve to the present-day structure of a flat segment of the subducting Nazca plate

Division and subtraction by distinct cortical inhibitory networks in vivo

Brain circuits process information through specialized neuronal subclasses interacting within a network. Revealing their interplay requires activating specific cells while monitoring others in a functioning circuit. Here we use a new platform for two-way light-based circuit interrogation in visual cortex in vivo to show the computational implications of modulating different subclasses of inhibitory neurons during sensory processing. We find that soma-targeting, parvalbumin-expressing (PV) neurons principally divide responses but preserve stimulus selectivity, whereas dendrite-targeting, somatostatin-expressing (SOM) neurons principally subtract from excitatory responses and sharpen selectivity. Visualized in vivo cell-attached recordings show that division by PV neurons alters response gain, whereas subtraction by SOM neurons shifts response levels. Finally, stimulating identified neurons while scanning many target cells reveals that single PV and SOM neurons functionally impact only specific subsets of neurons in their projection fields. These findings provide direct evidence that inhibitory neuronal subclasses have distinct and complementary roles in cortical computations.National Institutes of Health (U.S.) (Postdoctoral Fellowship)Simons Foundation (Postdoctoral Fellowship)National Institutes of Health (U.S.) (Predoctoral Fellowship

Bone Health Improvement Protocol

Introduction. Metabolic bone disease is a malady that causessignificant morbidity and mortality to a patient who has sustaineda fragility fracture. There is currently no protocol toprevent secondary fragility fracture at our institution. The objectiveof this study was to create an appropriate protocol forimplementing clinical pathways for physicians to diagnose andtreat osteoporosis and fragility fractures by educating patients. Methods. A multidisciplinary team created an appropriateprotocol that could be implemented in an inpatient setting.A thorough literature review was conducted to evaluatepotential barriers and efficacious methods of protocol design. Results. A bone health improvement protocol was developed.Any patient over the age of 50 who sustains a fracture from lowenergy trauma, such as a fall from standing or less, should beconsidered to place into this protocol. These patients receivededucation on metabolic bone disease, a prescription for highdose vitamin D therapy, and laboratory testing to determinethe etiology of their metabolic bone disease. Continuity of careof these patients with their primary care provider was providedfor further management of their metabolic bone disease andevaluation of their disease after discharged from the hospital. Conclusion. Comprehensive secondary prevention should consistof osteoporosis assessment and treatment together with afall risk assessment. With this protocol, secondary fragility fracturespotentially could be prevented. KS J Med 2017;10(3):62-66

A divergence free C0C^0-RIPG stream function formulation of the incompressible Stokes system with variable viscosity

Pointwise divergence free velocity field approximations of the Stokes system are gaining popularity due to their necessity in precise modelling of physical flow phenomena. Several methods have been designed to satisfy this requirement; however, these typically come at a greater cost when compared with standard conforming methods, for example, because of the complex implementation and development of specialized finite element bases. Motivated by the desire to mitigate these issues for 2D simulations, we present a $C^0$-interior penalty Galerkin (IPG) discretization of the Stokes system in the stream function formulation. In order to preserve a spatially varying viscosity this approach does not yield the standard and well known biharmonic problem. We further employ the so-called robust interior penalty Galerkin (RIPG) method; stability and convergence analysis of the proposed scheme is undertaken. The former, which involves deriving a bound on the interior penalty parameter is particularly useful to address the $\mathcal{O}(h^{-4})$ growth in the condition number of the discretized operator. Numerical experiments confirming the optimal convergence of the proposed method are undertaken. Comparisons with thermally driven buoyancy mantle convection model benchmarks are presented