Natural History of Autosomal Recessive Spastic Ataxia of Charlevoix-Saguenay: a 4-Year Longitudinal Study.

Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) is a neurologic disorder with generally well-known clinical manifestations. However, few studies assessed their progression rate using a longitudinal design. This study aimed to document the natural history of ARSACS over a 4-year period in terms of upper and lower limb functions, balance, walking capacity, performance in daily living activities, and disease severity. Forty participants were assessed on three occasions over 4 years. Participant performance was reported in raw data as well as in percentage from reference values to consider the normal aging process. Severe balance and walking capacity impairments were found, with a significant performance decrease over the 4 years. Balance reached a floor score of around 6 points on the Berg Balance Scale for participants aged >40 years, while other participants lost about 1.5 points per year. The mean loss in walking speed was 0.044 m/s per year and the mean decrease in the distance walked in 6 min was 20.8 m per year for the whole cohort. Pinch strength, balance, walking speed, and walking distance decreased over time even when reported in percentage from reference values. Major impairments and rapid progression rates were documented in the present study for upper limb coordination, pinch strength, balance, and walking capacity in the ARSACS population. A progression rate beyond the normal aging process was observed. These results provide fundamental insights regarding the disease prognosis that will help to better inform patients, develop specific rehabilitation programs, and improve trial readiness.

Toward a Better Understanding of Walking Speed in Ataxia of Charlevoix-Saguenay: a Factor Exploratory Study.

Mobility limitations, including a decrease in walking speed, are major issues for people with autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS). Improving our understanding of factors influencing walking speed in ARSACS may inform the development of future interventions for gait rehabilitation and contribute to better clinical practices. The objective of the study was to identify the factors influencing the self-selected walking speed in adults with ARSACS. The dependent variable of this cross-sectional study was the self-selected speed and the factors (independent variables) were age, sex, balance, balance confidence, knee flexion and extension cocontraction indexes, lower limb coordination, passive range of motion of ankle dorsiflexion, knee and hip extension, and global spasticity. Multiple regression models were used to assess the relationships between walking speed and each factor individually. Six factors were significantly associated with walking speed and thus included in regression models. The models explained between 42.4 and 66.5% of the total variance of the self-selected walking speed. The factors that most influence self-selected walking speed are balance and lower limb coordination. In order of importance, the other factors that also significantly influence self-selected walking speed are ankle dorsiflexion range of motion, lower limb spasticity, knee extension range of motion, and confidence in balance. Balance and lower limb coordination should be targeted in rehabilitation interventions to maintain walking ability and functional independence as long as possible. The six factors identified should also be included in future studies to deepen our understanding of walking speed.

Measurement of Near-Field Radiative Heat Transfer at Deep Sub-Wavelength Distances using Nanomechanical Resonators.

Near-field radiative heat transfer (NFRHT) measurements often rely on custom microdevices that can be difficult to reproduce after their original demonstration. Here we study NFRHT using plain silicon nitride (SiN) membrane nanomechanical resonators─a widely available substrate used in applications such as electron microscopy and optomechanics─and on which other materials can easily be deposited. We report measurements down to a minimal distance of 180 nm between a large radius of curvature (15.5 mm) glass radiator and a SiN membrane resonator. At such deep sub-wavelength distance, heat transfer is dominated by surface polariton resonances over a (0.25 mm)2 effective area, which is comparable to plane-plane experiments employing custom microfabricated devices. We also discuss how measurements using nanomechanical resonators create opportunities for simultaneously measuring near-field radiative heat transfer and thermal radiation forces (e.g., thermal corrections to Casimir forces).

Wheelchair mobility, motor performance and participation of adult wheelchair users with ARSACS: a cross-sectional study.

PURPOSE: Although approximately 45% of adults with Autosomal Recessive Spastic Ataxia of Charlevoix-Saguenay (ARSACS) are permanent wheelchair users, this sub population has been less studied. The purpose of this study was to document wheelchair mobility, motor performance, and participation in a cohort of adult wheelchair users with ARSACS. METHODS: We recruited 36 manual and powered wheelchair users with ARSACS, aged between 34 and 64 years, for this cross-sectional study. Participants completed measures regarding wheelchair mobility (Wheelchair Skills Test Questionnaire [WST-Q-F], Wheelchair Use Confidence Scale [WheelCon-F] and Wheelchair Outcome Measure [WhOM-F]), motor performance (Scale for the Assessment and Rating of Ataxia [SARA], Disease Severity Index for adults with ARSACS [DSI-ARSACS], Upper Extremity Performance Test for the Elderly [TEMPA], Standardised Finger to Nose Test [SFNT], grip strength, pinch strength, Lower Extremity Motor Coordination Test [LEMOCOT], Berg Balance Scale [BBS], Timed Up and Go [TUG] and 10-meter Walk Test [10mWT]), and participation (Barthel Index, LSA-F and LIFE-H). Results were compared between age groups (≤49 years and ≥50 years), types of wheelchair used, and available reference values. Correlations were computed between wheelchair mobility, upper limb function, and participation. RESULTS: Participants presented limitations regarding wheelchair skills, motor performance, and participation in daily activities. Despite preserved upper limb strength, wheelchair skills, upper and lower limb coordination, standing balance, and functional independence were generally more impaired after 50 years of age and among powered wheelchair users. Significant moderate correlations were found between wheelchair skills and self-efficacy, upper limb strength and coordination, and participation in daily and social activities. CONCLUSIONS: This study provided the first data sets describing specific characteristics of manual and powered wheelchair users with ARSACS. It supports a need to offer wheelchair skills training interventions to adults with ARSACS, which could increase their daily and social participation.IMPLICATIONS FOR REHABILITATIONAdult wheelchair users with ARSACS present with limited wheelchair skills, significantly impaired motor performance, and reduced participation that generally decreases with age. This profile may serve as comparative data for clinicians to anticipate disease progression.This study provides the first data on distinguishing characteristics between PWC users and MWC users with ARSACS. The main characteristics of PWC users include more severe functional limitations and motor impairments, as well as limited grip strength that contrasts with the general preservation of this function among other adults with ARSACS.There is a need to offer and evaluate wheelchair skills training interventions in the future for adults with ARSACS. The general preservation of grip and pinch strength observed in this population suggests a potential for improvement. Considering the associations found between wheelchair mobility and participation, such interventions may increase users' daily and social participation.

Characterizing the biomechanical differences between novice and expert point-of-care ultrasound practitioners using a low-cost gyroscope and accelerometer integrated sensor: A pilot study.

Introduction: Point-of-care ultrasound (POCUS) has become an important diagnostic tool in acute care medicine; however, little is known about the biomechanical differences between novice and expert practitioners. Methods: A low-cost ($50 CAD) gyroscope and accelerometer integrated sensor was assembled and affixed to an ultrasound probe. Seventeen participants, nine novices and eight experts, were recruited to perform three abdominal and four cardiac scans on a standardized patient. Participant demographics, time per scan, average acceleration, average angular velocity, decay in acceleration and angular velocity over time, and frequency of probe movements were analyzed. Video capture with blinded video review was scored. Results: On video review, experts had higher image optimization and acquisition scores for both abdominal and cardiac scans. Experts had shorter scan times for abdominal (7 s vs. 26 s, p = 0.003) and cardiac (11 s vs. 26 s, p < 0.001) scans. There was no difference in average acceleration (g) between novices and experts performing abdominal (1.02 vs. 1.01, p = 0.50) and cardiac (1.01 vs. 1.01, p = 0.45) scans. Experts had lower angular velocity (°/s) for abdominal scans (10.00 vs. 18.73, p < 0.001) and cardiac scans (15.61 vs. 20.33, p = 0.02) There was a greater decay in acceleration over time for experts performing cardiac scans compared to novices (-0.194 vs. -0.050, p = 0.03) but not for abdominal scans or when measuring angular velocity. The frequency of movements (Hz) was higher for novices compared to experts for abdominal (16.68 vs. 13.79, p < 0.001) and cardiac (17.60 vs. 13.63, p = 0.002) scans. Discussion: This study supports the feasibility of a low-cost gyroscope and accelerometer integrated sensor to quantify the biomechanics of POCUS. It may also support the concept of "window shopping" as a method by which experts obtain abdominal and cardiac views, where sliding is used to find an acoustic window, then smaller rocking and tilting probe movements are used to refine the image.

Functional mobility in walking adult population with ataxia of Charlevoix-Saguenay.

BACKGROUND: This study aimed to describe lower limbs impairments, balance and activity limitations related to indoor mobility in adult walkers with autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS). RESULTS: Twenty-five participants were recruited with a mean age of 32.2 (± 10.4) years with 45.7% using a walking aid. There is a significant difference between participants with and without a walking aid in terms of lower limbs coordination, balance and mobility. Although participants who walk without a walking aid perform better than the others and they are below predictive or reference values. Despite significant mobility limitations, only mild spasticity and passive range of motion limitations were observed. However, there is a significant difference between unaffected individuals and participants with ARSACS for lower limb muscle cocontraction. CONCLUSIONS: Results show a high level of lower limb impairments, balance and mobility limitation in adults' participants with ARSACS that are still walking, including people not using a walking aid. One of the most original finding is the presence of excessive cocontraction and a relatively mild level of spasticity in the lower limbs muscles. Results of this study better circumscribes the impairments and activities that should be the focus of intervention including rehabilitation in ARSACS.

tDCS Task-Oriented Approach Improves Function in Individuals With Fibromyalgia Pain. A Pilot Study.

Fibromyalgia (FM) is a complex pain syndrome accompanied by physical disability and loss of daily life activities. Evidences suggest that modulation of the primary motor cortex (M1) by transcranial direct current stimulation (tDCS) improves functional physical capacity in chronic pain conditions. However, the gain on physical function in people living with FM receiving tDCS is still unclear. This study aimed to evaluate whether the tDCS task-oriented approach improves function and reduces pain in a single cohort of 10 FM. A total of 10 women with FM (60.4 ± 15.37 years old) were enrolled in an intervention including anodal tDCS delivered on M1 (2 mA from a constant stimulator for 20 min); simultaneously they performed a functional task. The anode was placed on the contralateral hemisphere of the dominant hand. Outcome assessments were done before the stimulation, immediately after stimulation and 30 min after the end of tDCS. The same protocol was applied in subsequent sessions. A total of five consecutive days of tDCS were completed. The main outcomes were the number of repetitions achieved and time in active practice to evaluate functional physical task performance such as intensity of the pain (visual analog scale) and level of fatigue (Borg scale). After 5 days of tDCS, the number of repetitions achieved significantly increased by 49% (p = 0.012). No change was observed in active practice time. No increase in pain was observed despite the mobility of the painful parts of the body. These results are encouraging since an increase in pain due to the mobilization of painful body parts could have been observed at the end of the 5th day of the experiment. These results support the use of tDCS in task-based rehabilitation.

Integrated near-field thermo-photovoltaics for heat recycling.

Energy transferred via thermal radiation between two surfaces separated by nanometer distances can be much larger than the blackbody limit. However, realizing a scalable platform that utilizes this near-field energy exchange mechanism to generate electricity remains a challenge. Here, we present a fully integrated, reconfigurable and scalable platform operating in the near-field regime that performs controlled heat extraction and energy recycling. Our platform relies on an integrated nano-electromechanical system that enables precise positioning of a thermal emitter within nanometer distances from a room-temperature germanium photodetector to form a thermo-photovoltaic cell. We demonstrate over an order of magnitude enhancement of power generation (Pgen ~ 1.25 µWcm-2) in our thermo-photovoltaic cell by actively tuning the gap between a hot-emitter (TE ~ 880 K) and the cold photodetector (TD ~ 300 K) from ~ 500 nm down to ~ 100 nm. Our nano-electromechanical system consumes negligible tuning power (Pgen/PNEMS ~ 104) and relies on scalable silicon-based process technologies.

Broadband enhancement of thermal radiation.

Broadband thermal radiation sources are critical for various applications including spectroscopy and electricity generation. However, due to the difficulty in simultaneously achieving high absorptivity and low thermal mass these sources are inefficient. We show a platform that enables one to obtain enhanced emission by coupling a thermal emitter to an optical cavity. We experimentally demonstrate broadband enhancement of thermal emission between λ ~2 ̶ 4.2 µm using an inherently poor thermal emitter consisting of tens of nanometers thick SiC film with 10% emissivity (εSiC ~0.1). We measure over twofold enhancement of total emission power over the entire spectral band and threefold enhancement of thermal emission over 3 to 3.4 µm. Our platform has the potential to enable development of ideal blackbody sources operating at substantially lower heating powers.

An exploratory natural history of ataxia of Charlevoix-Saguenay: A 2-year follow-up.

OBJECTIVE: To document the decline of upper and lower limb functions, mobility, and independence in daily living activities in adults with autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) over a 2-year period. METHODS: An exploratory longitudinal design was used. Nineteen participants were assessed on 2 occasions 2 years apart. Assessments included the Standardized Finger Nose Test, Nine-Hole Peg Test, Lower Extremity Motor Coordination Test, Berg Balance Scale, 10-m walk test (10mWT), 6-minute walk test (6MWT), Scale for the Assessment and Rating of Ataxia (SARA), and Barthel Index. RESULTS: A significant decline was observed between baseline and follow-up for lower limb coordination, balance, walking abilities (10mWT and 6MWT), and overall disease severity (SARA). All differences were beyond measurement error documented in ARSACS. Results showed no significant decline for upper limb coordination and fine dexterity performance. CONCLUSION: Although ARSACS is a slow, progressive disease, results showed that mobility, balance, and lower limb performance significantly decreased over the 2-year period and that selected outcome measures were able to capture this decline beyond measurement errors.

On-chip thermo-optic tuning of suspended microresonators.

Suspended optical microresonators are promising devices for on-chip photonic applications such as radio-frequency oscillators, optical frequency combs, and sensors. Scaling up these devices demands the capability to tune the optical resonances in an integrated manner. Here, we design and experimentally demonstrate integrated on-chip thermo-optic tuning of suspended microresonators by utilizing suspended wire bridges and microheaters. We demonstrate the ability to tune the resonance of a suspended microresonator in silicon nitride platform by 9.7 GHz using 5.3 mW of heater power. The loaded optical quality factor (QL ~92,000) stays constant throughout the detuning. We demonstrate the efficacy of our approach by completely turning on and off the optical coupling between two evanescently coupled suspended microresonators.

Hot Carrier-Based Near-Field Thermophotovoltaic Energy Conversion.

Near-field thermophotovoltaics (NFTPV) is a promising approach for direct conversion of heat to electrical power. This technology relies on the drastic enhancement of radiative heat transfer (compared to conventional blackbody radiation) that occurs when objects at different temperatures are brought to deep subwavelength distances (typically <100 nm) from each other. Achieving such radiative heat transfer between a hot object and a photovoltaic (PV) cell could allow direct conversion of heat to electricity with a greater efficiency than using current solid-state technologies (e.g., thermoelectric generators). One of the main challenges in the development of this technology, however, is its incompatibility with conventional silicon PV cells. Thermal radiation is weak at frequencies larger than the ∼1.1 eV bandgap of silicon, such that PV cells with lower excitation energies (typically 0.4-0.6 eV) are required for NFTPV. Using low bandgap III-V semiconductors to circumvent this limitation, as proposed in most theoretical works, is challenging and therefore has never been achieved experimentally. In this work, we show that hot carrier PV cells based on Schottky junctions between silicon and metallic films could provide an attractive solution for achieving high efficiency NFTPV electricity generation. Hot carrier science is currently an important field of research and several approaches are investigated for increasing the quantum efficiency (QE) of hot carrier generation beyond conventional Fowler model predictions. If the Fowler limit can indeed be overcome, we show that hot carrier-based NFTPV systems-after optimization of their thermal radiation spectrum-could allow electricity generation with up to 10-30% conversion efficiencies and 10-500 W/cm2 generated power densities (at 900-1500 K temperatures). We also discuss how the unique properties of thermal radiation in the extreme near-field are especially well suited for investigating recently proposed approaches for high QE hot carrier junctions. We therefore expect our work to be of interest for the field of hot carrier science and-by relying solely on conventional thin film materials-to provide a path for the experimental demonstration of NFTPV energy conversion.

Near-field radiative heat transfer between parallel structures in the deep subwavelength regime.

Thermal radiation between parallel objects separated by deep subwavelength distances and subject to large thermal gradients (>100 K) can reach very high magnitudes, while being concentrated on a narrow frequency distribution. These unique characteristics could enable breakthrough technologies for thermal transport control and electricity generation (for example, by radiating heat exactly at the bandgap frequency of a photovoltaic cell). However, thermal transport in this regime has never been achieved experimentally due to the difficulty of maintaining large thermal gradients over nanometre-scale distances while avoiding other heat transfer mechanisms, namely conduction. Here, we show near-field radiative heat transfer between parallel SiC nanobeams in the deep subwavelength regime. The distance between the beams is controlled by a high-precision micro-electromechanical system (MEMS). We exploit the mechanical stability of nanobeams under high tensile stress to minimize thermal buckling effects, therefore keeping control of the nanometre-scale separation even at large thermal gradients. We achieve an enhancement of heat transfer of almost two orders of magnitude with respect to the far-field limit (corresponding to a 42 nm separation) and show that we can maintain a temperature gradient of 260 K between the cold and hot surfaces at ∼100 nm distance.

Demonstration of strong near-field radiative heat transfer between integrated nanostructures.

Near-field heat transfer recently attracted growing interest but was demonstrated experimentally only in macroscopic systems. However, several projected applications would be relevant mostly in integrated nanostructures. Here we demonstrate a platform for near-field heat transfer on-chip and show that it can be the dominant thermal transport mechanism between integrated nanostructures, overcoming background substrate conduction and the far-field limit (by factors 8 and 7, respectively). Our approach could enable the development of active thermal control devices such as thermal rectifiers and transistors.