Handwriting at Different Paces and Sizes With Visual Cues in Persons With Parkinson’s Disease

Background: Persons with Parkinson’s disease (PD) typically have small handwriting, especially when writing faster and/or larger. However, visual cues can help persons with PD increase their handwriting size. This study tested if lined paper would improve handwriting in persons with PD, even when writing faster and/or larger. Secondarily, we wanted determine if persons with PD perceived handwriting as stressful, and if perceived stress was associated with writing performance. Methods: The study included 22 subjects with Parkinson’s disease and 11 age-gender-matched controls. Participants completed eight trials (2 × 2 × 2) of printing a “P” and “d”, at a comfortable speed and also as fast as possible in two different sizes (1, 2 cm). The participants wrote with a ballpoint pen on lined paper. Bipolar electromyography (EMG) sensors recorded muscle activity from the index finger extensor (extensor digitorum communis (EDC)) and flexor (first dorsal interosseous (FDI)). Participants completed all of the trials for a particular pace (conditions were randomized) before completing all the trials of the other pace (order was counterbalanced). Results: Handwriting height was smaller for persons with PD when required to write fast. There was also a trend for patients with PD to write slower and have smaller peak pen accelerations, but these were not statistically significant. Persons with PD found handwriting to be more stressful than healthy older adults did; and perceived stress negatively correlated with letter height and EMG activity. Conclusions: Our study found that visual cues did not normalize handwriting height in persons with PD when writing large and/or fast. Persons with PD find handwriting to be stressful, and stress may negatively influence their handwriting

Covalently bonded interfaces for polymer/graphene composites

The interface is well known for taking a critical role in the determination of the functional and mechanical properties of polymer composites. Previous interface research has focused on utilising reduced graphene oxide that is limited by a low structural integrity, which means a high fraction is needed to produce electrically conductive composites. By using 4,40-diaminophenylsulfone, we in this study chemically modified high-structural integrity graphene platelets (GnPs) of 2–4 nm in thickness, covalently bonded GnPs with an epoxy matrix, and investigated the morphology and functional and mechanical performance of these composites. This covalently bonded interface prevented GnPs stacking in the matrix. In comparison with unmodified composites showing no reduction in electrical volume resistivity, the interface-modified composite at 0.489 vol% GnPs demonstrates an eight-order reduction in the resistivity, a 47.7% further improvement in modulus and 84.6% in fracture energy release rate. Comparison of GnPs with clay and multi-walled carbon nanotubes shows that our GnPs are more advantageous in terms of performance and cost. This study provides a novel method for developing interface-tuned polymer/graphene composites

Repetitive finger movement and circle drawing in persons with Parkinson’s disease

Little is known regarding how repetitive finger movement performance impacts other fine motor control tasks, such as circle drawing, in persons with Parkinson’s disease (PD). Previous research has shown that impairments in repetitive finger movements emerge at rates near to and above 2 Hz in most persons with PD. Thus, the purpose of this study was to compare circle drawing performance in persons with PD that demonstrate impairment in repetitive finger movement and those that do not. Twenty-two participants with PD and twelve healthy older adults completed the study. Only participants with PD completed the repetitive finger movement task. From the kinematic data for the repetitive finger movement task, participants were grouped into Hasteners and Non-Hasteners. Participants with PD and the healthy older adults completed a series of circle drawing tasks at two different target sizes (1 cm and 2 cm) and three pacing conditions (Self-paced, 1.25 Hz, and 2.5 Hz). Kinematic and electromyography data were recorded and compared between groups. Results revealed that, in general, persons with PD demonstrate impairments in circle drawing and associated electromyography activity compared to healthy older adults. Moreover, persons with PD that hasten during repetitive finger movements demonstrate significantly increased movement rate during circle drawing, while those persons with PD that do not hasten demonstrate a significant increase in width variability. This suggests that differing motor control mechanisms may play a role in the performance of fine motor tasks in persons with PD. Continued research is needed to better understand differences in circle drawing performance among persons with PD to inform future development of patient-centered treatments

Development of polymer composites using modified, high-structural integrity graphene platelets

Previous studies on polymer/graphene composites have mainly utilized either reduced graphene oxide or graphite nanoplatelets of over 10 nm in thickness. In this study we covalently modified 3-nm thick graphene platelets (GnPs) by the reaction between the GnPs’ epoxide groups and the end-amine groups of a commercial long-chain surfactant (Mw = 2000), compounded the modified GnPs (m-GnPs) with a model polymer epoxy, and investigated the structure and properties of both m-GnPs and their epoxy composites. A low Raman ID/IG ratio of 0.13 was found for m-GnPs corresponding to high structural integ-rity. A percolation threshold of electrical conductivity was observed at 0.32 vol% m-GnPs, and the 0.98 vol% m-GnPs improved the Young’s modulus, fracture energy release rate and glass transition tem-perature of epoxy by 14%, 387% and 13%, respectively. These significantly improved properties are cred-ited to: (i) the low Raman ID/IG ratio of GnPs, maximizing the structural integrity and thus conductivity, stiffness and strength inherited from its sister graphene, (ii) the low thickness of GnPs, minimizing the damaging effect of the poor through-plane mechanical properties and electrical conductivity of graphene,(iii) the high-molecular weight surfactant, leading to uniformly dispersed GnPs in the matrix, and (iv) a covalently bonded interface between m-GnPs and matrix, more effectively transferring load/electron across interface

Melt compounding with graphene to develop functional, high-performance elastomers

Rather than using graphene oxide, which is limited by a high defect concentration and cost due to oxidation and reduction, we adopted cost-effective, 3.56 nm thick graphene platelets (GnPs) of high structural integrity to melt compound with an elastomer—ethylene–propylene–diene monomer rubber (EPDM)—using an industrial facility. An elastomer is an amorphous, chemically crosslinked polymer generally having rather low modulus and fracture strength but high fracture strain in comparison with other materials; and upon removal of loading, it is able to return to its original geometry, immediately and completely. It was found that most GnPs dispersed uniformly in the elastomer matrix, although some did form clusters. A percolation threshold of electrical conductivity at 18 vol% GnPs was observed and the elastomer thermal conductivity increased by 417% at 45 vol% GnPs. The modulus and tensile strength increased by 710% and 404% at 26.7 vol% GnPs, respectively. The modulus improvement agrees well with the Guth and Halpin-Tsai models. The reinforcing effect of GnPs was compared with silicate layers and carbon nanotube. Our simple fabrication would prolong the service life of elastomeric products used in dynamic loading, thus reducing thermosetting waste in the environment

Melt compounding with graphene to develop functional, high-performance elastomers

Rather than using graphene oxide, which is limited by a high defect concentration and cost due to oxidation and reduction, we adopted cost-effective, 3.56 nm thick graphene platelets (GnPs) of high structural integrity to melt compound with an elastomer—ethylene–propylene–diene monomer rubber (EPDM)—using an industrial facility. An elastomer is an amorphous, chemically crosslinked polymer generally having rather low modulus and fracture strength but high fracture strain in comparison with other materials; and upon removal of loading, it is able to return to its original geometry, immediately and completely. It was found that most GnPs dispersed uniformly in the elastomer matrix, although some did form clusters. A percolation threshold of electrical conductivity at 18 vol% GnPs was observed and the elastomer thermal conductivity increased by 417% at 45 vol% GnPs. The modulus and tensile strength increased by 710% and 404% at 26.7 vol% GnPs, respectively. The modulus improvement agrees well with the Guth and Halpin-Tsai models. The reinforcing effect of GnPs was compared with silicate layers and carbon nanotube. Our simple fabrication would prolong the service life of elastomeric products used in dynamic loading, thus reducing thermosetting waste in the environment

Design Tradeoffs and Challenges of Omnidirectional Optical Antenna for High Speed, Long Range Inter CubeSat Data Communication

Omnidirectional Optical Antennas (OOA) with 360o Field of Regard along with full-duplex laser communication capability can play a remarkable role in achieving sophisticated CubeSat mission that can achieve high speed (≥1Gbps), long distance (≥50km) data communication, data relaying among CubeSats and that processes formation flying ability. In this paper, we discuss miniature optical antenna design optimization techniques using COTS components to facilitate OOA development. In particular, we present challenges involving design tradeoffs among scanning mirror size, scanning angle, transmit beam width, beam divergence, pointing accuracy requirements and component availability in a SWaP-C limited system. We show that to achieve maximum SNR at long distance, the transmit laser beam diameter to mirror diameter ratio needs to be 0.8-0.9. Moreover, we show that the peak intensity varies and can decrease up to 70% over the mirror scanning range depending on transmitter beam size. Furthermore, we explain the effect of laser peak power, initial beam size and communication distance on Effective Communication Beam Width (ECBW) to maintain SNR≥10dB at 1Gb/s. We show that by choosing the optimum components and parameters an ECBW of ≥50m at 50km distance is achievable. Therefore, the communication link can endure angular disturbance of 50 μrad - 180.5 μrad

Stroboscopic Augmented Reality as an Approach to Mitigate Gravitational Transition Effects During Interplanetary Spaceflight

During interplanetary spaceflight, periods of extreme gravitational transitions will occur such as transitions between hypergravity, hypogravity, and microgravity. Following gravitational transitions, rapid sensorimotor adaptation or maladaptation may occur which can affect gaze control and weaken dynamic visual acuity in astronauts. A reduction in dynamic visual acuity during spaceflight could possibly impact or impair mission critical activities (e.g., control of extraterrestrial machinery/vehicles and other important tasks). Stroboscopic visual training is an emerging visual tool that has been terrestrially observed to enhance visual performance and perception by performing tasks under conditions of intermittent vision. This technique has also been seen to increase the dynamic visual acuity for individuals terrestrially. To mitigate the decreased dynamic visual acuity that is observed in astronauts following gravitational transitions, stroboscopic vision training may serve as a potential countermeasure. We describe the effects of gravitational transitions on the vestibulo-ocular system and dynamic visual acuity, review terrestrial stroboscopic visual training, and report the novel development of stroboscopic augmented reality as a possible countermeasure for G-transitions in future spaceflight

From carbon nanotubes and silicate layers to graphene platelets for polymer nanocomposites

In spite of extensive studies conducted on carbon nanotubes and silicate layers for their polymer-based nanocomposites, the rise of graphene now provides a more promising candidate due to its exceptionally high mechanical performance and electrical and thermal conductivities. The present study developed a facile approach to fabricate epoxy–graphene nanocomposites by thermally expanding a commercial product followed by ultrasonication and solution-compounding with epoxy, and investigated their morphologies, mechanical properties, electrical conductivity and thermal mechanical behaviour. Graphene platelets (GnPs) of 3.5