Matching Items (28)

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Improving health-care delivery in low-resource settings with nanotechnology: Challenges in multiple dimensions

Description

In the two decades after 1990, the rates of child and maternal mortality dropped by over 40% and 47%, respectively. Despite these improvements, which are in part due to increased

In the two decades after 1990, the rates of child and maternal mortality dropped by over 40% and 47%, respectively. Despite these improvements, which are in part due to increased access to medical technologies, profound health disparities exist. In 2015, a child born in a developing region is nearly eight times as likely to die before the age of 5 than one born in a developed region and developing regions accounted for nearly 99% of the maternal deaths. Recent developments in nanotechnology, however, have great potential to ameliorate these and other health disparities by providing new cost-effective solutions for diagnosis or treatment of a variety of medical conditions. Affordability is only one of the several challenges that will need to be met to translate new ideas into a medical product that addresses a global health need. This article aims to describe some of the other challenges that will be faced by nanotechnologists who seek to make an impact in low-resource settings across the globe.

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Date Created
  • 2017-03-29

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Effects of deep brain stimulation amplitude on motor performance in Parkinson’s disease

Description

Background: The efficacy of deep brain stimulation (DBS) in Parkinson’s disease has been convincingly demonstrated in studies comparing motor performance with and without stimulation, but characterization of the stimulation dose-response

Background: The efficacy of deep brain stimulation (DBS) in Parkinson’s disease has been convincingly demonstrated in studies comparing motor performance with and without stimulation, but characterization of the stimulation dose-response curves has been limited.
Methods: In a series of case studies, eight subjects with Parkinson’s disease and bilateral DBS systems were evaluated at their clinically determined stimulation (CDS) and at three reduced amplitudes, ie, approximately 70%, 30%, and 0% of the CDS (MOD, LOW, and OFF, respectively). Performance was assessed using the motor section of the Unified Parkinson’s Disease Rating Scale (UPDRS-III), which includes subscores for tremor, bradykinesia, gait, posture, and tapping. Data at the reduced settings were analyzed to determine if individual subjects demonstrated a threshold-like response, which was defined as a dose-response curve in which one decrement in stimulation accounted for ≥70% of the maximum change observed. Day-to-day variability was assessed using the CDS data from the three different days.
Results: In the dose-response curves, two subjects exhibited a threshold-like response, four exhibited a graded change, and two did not exhibit substantial changes. For some subjects, variability in CDS performance across the three days exceeded the change observed when reducing amplitude to the MOD setting. Comparisons across this set of eight subjects demonstrated that the mean UPDRS-III and all but one subscore significantly increased (performance degraded) when amplitude was reduced from CDS to the LOW and OFF conditions, but there were no significant changes when amplitude was reduced from CDS to the MOD condition.
Conclusion: Individual differences in the DBS dose-response curves may provide opportunities to optimize clinical performance. Day-to-day variability in motor performance cautions against the use of a single UPDRS measurement in clinical selection of DBS settings.

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  • 2012-12-11

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Adaptive control of ventilation using electrical stimulation in a biomechanical model

Description

Cervical spinal cord injury (SCI) causes loss or impairment of control of respiratory muscles. Life-sustaining ventilation can be provided by mechanical ventilators (which have numerous side effects) or open-loop electrical stimulation respiratory pacing systems.

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Date Created
  • 2015-12-18

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The effects of exercise on locomotor recovery after partial spinal cord injury in a rat model

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This study was conducted to examine the potential effects of exercise training on partial spinal cord injury on locomotor recovery in juvenile rats. Three groups were tested, where three female

This study was conducted to examine the potential effects of exercise training on partial spinal cord injury on locomotor recovery in juvenile rats. Three groups were tested, where three female Long-Evans rats 10-12 weeks of age were studied for their locomotion. All animals underwent a T8-T9 laminectomy and two of the three in each group received a dorsal, partial spinal cord injury. Locomotion was then analyzed every week, over 8-10 weeks. One of the two injured animals was given open access to a wheel after 2 weeks for voluntary exercise training. The results of this study suggested that injured animals displayed more irregular stepping patterns, larger hindlimb bases of support, greater and more variable interpaw distances, slower hindlimb speed, and increased dependency of swing-phase duty cycle on hindlimb speed. Trained animals displayed quicker recovery of stepping patterns, stepping of the hindpaw in relation to the preceding ipsilateral forepaw, and higher swing-duty cycle dependency on hindlimb speed in comparison to injured animals that did not receive exercise training. Due to a small sample size, there was a large amount of variation between individual animals in most parameters. These results are considered to be potential effects that may be seen in further study with a larger sample size. The research team will continue the research project to examine changes in neural pathways in the spinal cord and the effects of exercise on recovery after injury.

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Date Created
  • 2018-05

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Creating a Human-Powered Water Pump for the Maasai Community in Kenya and the Developing World: Creative Project

Description

The inception of the human-powered water pump began during my trip to Maasailand in Kenya over the Summer of 2017. Being one of the few Broadening the Reach of Engineering

The inception of the human-powered water pump began during my trip to Maasailand in Kenya over the Summer of 2017. Being one of the few Broadening the Reach of Engineering through Community Engagement (BRECE) Scholars at Arizona State University, I was given the opportunity to join Prescott College (PC) on their annual trip to the Maasai Education, Research, and Conservation (MERC) Institute in rural Kenya. The ASU BRECE scholars that choose to travel were asked to collaborate with the local Maasai community to help develop functional and sustainable engineering solutions to problems identified alongside community members using rudimentary technology and tools that were available in this resource-constrained setting. This initiative evolved into multiple projects from the installation of GravityLights (a local invention that powers LEDs with falling sandbags), the construction/installation of smokeless stoves, and development of a much-needed solution to move water from the rainwater collection tanks around camp to other locations. This last project listed was prototyped once in camp, and this report details subsequent iterations of this human-powered pump.

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Date Created
  • 2018-05

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Modeling the Effect of Mechanical Deformation on Electrical Stimulation of Peripheral Nerve Fibers

Description

There are many challenges in designing neuroprostheses and one of them is to maintain proper axon selectivity in all situations. This project is based on an electrode that is implanted

There are many challenges in designing neuroprostheses and one of them is to maintain proper axon selectivity in all situations. This project is based on an electrode that is implanted into a fascicle in a peripheral nerve and used to provide tactile sensory feedback of a prosthetic arm. This fascicle can undergo mechanical deformation during every day motion. This work aims to characterize the effect of fascicle deformation on axon selectivity and recruitment when electrically stimulated using hybrid modeling. The main framework consists of combining finite element modeling (FEM) and simulation environment NEURON. A suite of programs was developed to first populate a fascicle with axons followed by deforming the fascicle and rearranging axons accordingly. A model of the fascicle with an implanted electrode is simulated to find the electrical potential profile through FEM. The potential profile is then used to compare which axons are activated in the two conformations of the fascicle using NERUON.

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Date Created
  • 2021-05

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Development of a Wearable Haptic Feedback System for Use in Lower-Limb Prosthetics: Proof of Concept and Verification

Description

Skin and muscle receptors in the leg and foot provide able-bodied humans with force and position information that is crucial for balance and movement control. In lower-limb amputees however, this

Skin and muscle receptors in the leg and foot provide able-bodied humans with force and position information that is crucial for balance and movement control. In lower-limb amputees however, this vital information is either missing or incomplete. Amputees typically compensate for the loss of sensory information by relying on haptic feedback from the stump-socket interface. Unfortunately, this is not an adequate substitute. Areas of the stump that directly interface with the socket are also prone to painful irritation, which further degrades haptic feedback. The lack of somatosensory feedback from prosthetic legs causes several problems for lower-limb amputees. Previous studies have established that the lack of adequate sensory feedback from prosthetic limbs contributes to poor balance and abnormal gait kinematics. These improper gait kinematics can, in turn, lead to the development of musculoskeletal diseases. Finally, the absence of sensory information has been shown to lead to steeper learning curves and increased rehabilitation times, which hampers amputees from recovering from the trauma. In this study, a novel haptic feedback system for lower-limb amputees was develped, and studies were performed to verify that information presented was sufficiently accurate and precise in comparison to a Bertec 4060-NC force plate. The prototype device consisted of a sensorized insole, a belt-mounted microcontroller, and a linear array of four vibrotactile motors worn on the thigh. The prototype worked by calculating the center of pressure in the anteroposterior plane, and applying a time-discrete vibrotactile stimulus based on the location of the center of pressure.

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Created

Date Created
  • 2018-05

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Joint-specific changes in locomotor complexity in the absence of muscle atrophy following incomplete spinal cord injury

Description

Background
Following incomplete spinal cord injury (iSCI), descending drive is impaired, possibly leading to a decrease in the complexity of gait. To test the hypothesis that iSCI impairs gait coordination

Background
Following incomplete spinal cord injury (iSCI), descending drive is impaired, possibly leading to a decrease in the complexity of gait. To test the hypothesis that iSCI impairs gait coordination and decreases locomotor complexity, we collected 3D joint angle kinematics and muscle parameters of rats with a sham or an incomplete spinal cord injury.
Methods
12 adult, female, Long-Evans rats, 6 sham and 6 mild-moderate T8 iSCI, were tested 4 weeks following injury. The Basso Beattie Bresnahan locomotor score was used to verify injury severity. Animals had reflective markers placed on the bony prominences of their limb joints and were filmed in 3D while walking on a treadmill. Joint angles and segment motion were analyzed quantitatively, and complexity of joint angle trajectory and overall gait were calculated using permutation entropy and principal component analysis, respectively. Following treadmill testing, the animals were euthanized and hindlimb muscles removed. Excised muscles were tested for mass, density, fiber length, pennation angle, and relaxed sarcomere length.
Results
Muscle parameters were similar between groups with no evidence of muscle atrophy. The animals showed overextension of the ankle, which was compensated for by a decreased range of motion at the knee. Left-right coordination was altered, leading to left and right knee movements that are entirely out of phase, with one joint moving while the other is stationary. Movement patterns remained symmetric. Permutation entropy measures indicated changes in complexity on a joint specific basis, with the largest changes at the ankle. No significant difference was seen using principal component analysis. Rats were able to achieve stable weight bearing locomotion at reasonable speeds on the treadmill despite these deficiencies.
Conclusions
Decrease in supraspinal control following iSCI causes a loss of complexity of ankle kinematics. This loss can be entirely due to loss of supraspinal control in the absence of muscle atrophy and may be quantified using permutation entropy. Joint-specific differences in kinematic complexity may be attributed to different sources of motor control. This work indicates the importance of the ankle for rehabilitation interventions following spinal cord injury.

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Date Created
  • 2013-08-15

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A functional model and simulation of spinal motor pools and intrafascicular recordings of motoneuron activity in peripheral nerve

Description

Decoding motor intent from recorded neural signals is essential for the development of effective neural-controlled prostheses. To facilitate the development of online decoding algorithms we have developed a software platform

Decoding motor intent from recorded neural signals is essential for the development of effective neural-controlled prostheses. To facilitate the development of online decoding algorithms we have developed a software platform to simulate neural motor signals recorded with peripheral nerve electrodes, such as longitudinal intrafascicular electrodes (LIFEs). The simulator uses stored motor intent signals to drive a pool of simulated motoneurons with various spike shapes, recruitment characteristics, and firing frequencies. Each electrode records a weighted sum of a subset of simulated motoneuron activity patterns. As designed, the simulator facilitates development of a suite of test scenarios that would not be possible with actual data sets because, unlike with actual recordings, in the simulator the individual contributions to the simulated composite recordings are known and can be methodically varied across a set of simulation runs. In this manner, the simulation tool is suitable for iterative development of real-time decoding algorithms prior to definitive evaluation in amputee subjects with implanted electrodes. The simulation tool was used to produce data sets that demonstrate its ability to capture some features of neural recordings that pose challenges for decoding algorithms.

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Date Created
  • 2014-11-14

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Modelling the Response of Peripheral Nerve Axons to Applied Electric Fields

Description

Electrical stimulation can be used to activate peripheral nerve fibers to restore sensation to individuals with amputation and the technique is also being investigated as a means of treating a

Electrical stimulation can be used to activate peripheral nerve fibers to restore sensation to individuals with amputation and the technique is also being investigated as a means of treating a wide range of diseases. Longitudinal intrafascicular electrodes (LIFEs) are one of several types of electrodes that have been used to activate peripheral nerves. LIFEs can be used to activate small groups of fibers within a peripheral nerve fascicle, but the degree of their selectivity is uncertain. To investigate the effects of intrafascicular stimulation on nerve fiber activation, a mathematical, conductance-based model of an axon drawn from the literature was implemented and used to simulate the firing response of sensory nerve fibers in the presence of an applied monopolar electric field. Several axons were simulated to represent axons of different size, conductivity, spatial composition and location with respect to the electrode. Electric field profiles produced by pulses of different pulse widths and pulse amplitudes were created. Each fiber was placed within each resulting electric field and the firing threshold was determined. The effects of changes in pulse width, pulse amplitude, and distance on firing patterns were shown; all of these results were consistent with published experimental findings. The models showed lower firing threshold for smaller fibers than larger fibers and for fibers that were farther from the stimulating electrode than those that were closer. Firing threshold was also lower for stimuli of greater pulse width. Analysis of axon recruitment upon increases in pulse amplitude showed that the effects of fiber distance may be more pronounced than the effects of fiber size. This model can serve as a basis for further development to more accurately represent the effects of LIFEs and eventually may assist in the design of stimulation paradigms and waveforms to improve selectivity of axon activation when using LIFEs.

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Created

Date Created
  • 2019-05