Rovibrational Spectroscopy of Trans and Cis Conformers of 2-Furfural from High-Resolution Fourier Transform and QCL Infrared Measurements.

The ortho-isomer 2-furfural (2-FF), which is a primary atmospheric pollutant produced from biomass combustion, is also involved in oxidation processes leading to the formation of secondary organic aerosols. Its contribution to radiative forcing remains poorly understood. Thus, monitoring 2-FF directly in the atmosphere or in atmospheric simulation chambers to characterize its reactivity is merited. The present study reports an extensive jet-cooled rovibrational study of trans and cis conformers of 2-FF in the mid-IR region using two complementary setups: a continuous supersonic jet coupled to a high-resolution Fourier transform spectrometer on the IR beamline of the SOLEIL synchrotron (JET-AILES), and a pulsed jet coupled to a mid-IR tunable quantum cascade laser spectrometer (SPIRALES). Firstly, jet-cooled spectra recorded at rotational temperatures ranging between 20 and 50 K were exploited to derive reliable excited-state molecular parameters of trans- and cis-2-FF vibrational bands in the fingerprint region. The parameters were obtained from global fits of 11,376 and 3355 lines distributed over eight and three vibrational states (including the ground state), respectively, with a root mean square of 12 MHz. In a second step, the middle resolution spectrum of 2-FF recorded at 298.15 K and available in the HITRAN database was reconstructed by extrapolating the data derived from our low-temperature high-resolution analyses to determine the cross sections of each vibrational band of both 2-FF conformers in the 700-1800 cm-1 region. Finally, we clearly demonstrated that the contribution of hot bands observed in the room temperature 2-FF spectrum, estimated between 40 and 63% of the fundamental band, must be imperatively introduced in our simulation to correctly reproduce the HITRAN vibrational cross sections of 2-FF with a deviation smaller than 10%.

Millimeter-Wave Spectroscopy of Methylfuran Isomers: Local vs. Global Treatments of the Internal Rotation.

Methylfurans are methylated aromatic heterocyclic volatile organic compounds and primary or secondary pollutants in the atmosphere due to their capability to form secondary organic aerosols in presence of atmospheric oxidants. There is therefore a significant interest to monitor these molecules in the gas phase. High resolution spectroscopic studies of methylated furan compounds are generally limited to pure rotational spectroscopy in the vibrational ground state. This lack of results might be explained by the difficulties arisen from the internal rotation of the methyl group inducing non-trivial patterns in the rotational spectra. In this study, we discuss the benefits to assign the mm-wave rotational-torsional spectra of methylfuran with the global approach of the BELGI-Cs code compared to local approaches such as XIAM and ERHAM. The global approach reproduces the observed rotational lines of 2-methylfuran and 3-methylfuran in the mm-wave region at the experimental accuracy for the ground vt=0 and the first torsional vt=1 states with a unique set of molecular parameters. In addition, the V3 and V6 parameters describing the internal rotation potential barrier may be determined with a high degree of accuracy with the global approach. Finally, a discussion with other heterocyclic compounds enables the study of the influence of the electronic environment on the hindered rotation of the methyl group.

The Effect of Exoskeletal-Assisted Walking on Spinal Cord Injury Bowel Function: Results from a Randomized Trial and Comparison to Other Physical Interventions.

Bowel function after spinal cord injury (SCI) is compromised because of a lack of voluntary control and reduction in bowel motility, often leading to incontinence and constipation not easily managed. Physical activity and upright posture may play a role in dealing with these issues. We performed a three-center, randomized, controlled, crossover clinical trial of exoskeletal-assisted walking (EAW) compared to usual activity (UA) in people with chronic SCI. As a secondary outcome measure, the effect of this intervention on bowel function was assessed using a 10-question bowel function survey, the Bristol Stool Form Scale (BSS) and the Spinal Cord Injury Quality of Life (SCI-QOL) Bowel Management Difficulties instrument. Fifty participants completed the study, with bowel data available for 49. The amount of time needed for the bowel program on average was reduced in 24% of the participants after EAW. A trend toward normalization of stool form was noted. There were no significant effects on patient-reported outcomes for bowel function for the SCI-QOL components, although the time since injury may have played a role. Subset analysis suggested that EAW produces a greater positive effect in men than women and may be more effective in motor-complete individuals with respect to stool consistency. EAW, along with other physical interventions previously investigated, may be able to play a previously underappreciated role in assisting with SCI-related bowel dysfunction.

Exoskeletal-assisted walking may improve seated balance in persons with chronic spinal cord injury: a pilot study.

STUDY DESIGN: Pre-post intervention. OBJECTIVE: To explore the potential effect of exoskeletal-assisted walking (EAW) on seated balance for persons with chronic motor complete spinal cord injury (SCI). SETTING: A SCI research center. METHODS: Eight participants who were over 18 years of age with chronic SCI and used a wheelchair for mobility were enrolled. Seven able-bodied participants were used for normal seated balance comparative values. Participants with chronic SCI received supervised EAW training using a powered exoskeleton (ReWalkTM) for a median 30 sessions (range from 7 to 90 sessions). Before and after EAW training, seated balance testing outcomes were collected using computerized dynamic posturography, providing measurements of endpoint excursion (EPE), maximal excursion (MXE), and directional control (DCL). Modified functional reach test (MFRT) and the sub-scales of physical functioning and role limitations due to physical health from the Short Form (36) Health Survey (SF-36) were used to identify changes in functional activities. RESULTS: After EAW training, seated balance significantly improved in total-direction EPE and MXE (P < 0.01 and P < 0.017 respectively). The results of MFRT and sub-scales of physical functioning and role limitations due to physical health improved after EAW training but were not statistically significant. CONCLUSIONS: EAW training may have the potential to improve seated balance for persons with chronic motor complete SCI. Due to the limitations of the study, such as small sample size and lack of a control group, further studies are needed to clarify the effect of improving seated balance through EAW training.

Effect of Exoskeletal-Assisted Walking on Soft Tissue Body Composition in Persons With Spinal Cord Injury.

OBJECTIVE: To determine the effect of overground walking using a powered exoskeleton on soft tissue body composition in persons with spinal cord injury (SCI). DESIGN: A prospective, single group observational pilot study. SETTING: Medical center. PARTICIPANTS: Persons (N=8) with chronic (>6mo) SCI between 18 and 65 years old who weighed less than 100 kg. INTERVENTIONS: Overground ambulation training using a powered exoskeleton (ReWalk) for 40 sessions, with each session lasting up to 2 hours, with participants training 3 times per week. MAIN OUTCOME MEASURE(S): Dual-energy x-ray absorptiometry (DXA) was used to measure lean mass (LM) and fat mass (FM) from the whole body, arms, legs and trunk. DXA was also used to assess visceral adipose tissue (VAT). Walking performance was measured by 6-minute walk test. RESULTS: Participants significantly lost total body FM (-1.8±1.2kg, P=.004) with the loss of adiposity distributed over several regional sites. Six of the 8 participants lost VAT, with the average loss in VAT trending toward significance (-0.141kg, P=.06). LM for the group was not significantly changed. CONCLUSIONS: Sustained and weekly use of powered exoskeletons in persons with SCI has the potential to reduce FM with inferred improvements in health.

Oxygen Uptake During Exoskeletal-Assisted Walking in Persons With Paraplegia.

OBJECTIVE: To determine the cardiometabolic demands associated with exoskeletal-assisted walking (EAW) in persons with paraplegia. This study will further examine if training in the device for 60 sessions modifies cost of transport (CT). DESIGN: Prospective cohort study. Measurements over the course of a 60-session training program, approximately 20 sessions apart. SETTING: James J. Peters Bronx Veterans Affairs Medical Center, Center for the Medical Consequences of Spinal Cord Injury Research Center. PARTICIPANTS: The participants' demographics (N=5) were 37-61 years old, body mass index (calculated as weight in kilograms divided by height in meters squared) of 22.7-28.6, level of injury from T1-T11, and 2-14 years since injury. INTERVENTIONS: Powered EAW. MAIN OUTCOME MEASURES: Oxygen consumption per unit time (V˙O2, mL/min/kg), velocity (m/min), cost of transport (V˙O2/velocity), and rating of perceived exertion (RPE). RESULTS: With training: EAW velocity significantly improved (Pre: 51±51m; 0.14±0.14m/s vs Post: 99±42m; 0.28±0.12m/s, P=.023), RPE significantly decreased (Pre: 13±6 vs Post: 7±4, P=.001), V˙O2 significantly improved (Pre: 9.76±1.23 mL/kg/m vs Post: 12.73±2.30 mL/kg/m, P=.04), and CT was reduced from the early to the later stages of training (3.66±5.2 vs 0.87±0.85 mL/kg/m). CONCLUSIONS: The current study suggests that EAW training improves oxygen uptake efficiency and walking velocities, with a lower perception of exertion.

The design of a randomized control trial of exoskeletal-assisted walking in the home and community on quality of life in persons with chronic spinal cord injury.

There are more than 300,000 estimated cases of spinal cord injury (SCI) in the United States, and approximately 27,000 of these are Veterans. Immobilization from SCI results in adverse secondary medical conditions and reduced quality of life. Veterans with SCI who have completed rehabilitation after injury and are unable to ambulate receive a wheelchair as standard of care. Powered exoskeletons are a technology that offers an alternative form of limited mobility by enabling over-ground walking through an external framework for support and computer-controlled motorized hip and knee joints. Few studies have reported the safety and efficacy for use of these devices in the home and community environments, and none evaluated their impact on patient-centered outcomes through a randomized clinical trial (RCT). Absence of reported RCTs for powered exoskeletons may be due to a range of challenges, including designing, statistically powering, and conducting such a trial within an appropriate experimental framework. An RCT for the study of exoskeletal-assisted walking in the home and community environments also requires the need to address key factors such as: avoiding selection bias, participant recruitment and retention, training, and safety concerns, particularly in the home environment. These points are described here in the context of a national, multisite Department of Veterans Affairs Cooperative Studies Program-sponsored trial. The rationale and methods for the study design were focused on providing a template for future studies that use powered exoskeletons or other strategies for walking and mobility in people with immobilization due to SCI.

Synchrotron-Based High Resolution Far-Infrared Spectroscopy of trans-Butadiene.

The high resolution far-infrared spectrum of trans-butadiene has been reinvestigated by Fourier-transform spectroscopy at two synchrotron radiation facilities, SOLEIL and the Canadian Light Source, at temperatures ranging from 50 to 340 K. Beyond the well-studied bands, two new fundamental bands lying below 1100 cm-1, ν10 and ν24, have been assigned using a combination of cross-correlation (ASAP software) and Loomis-Wood type (LWWa software) diagrams. While the ν24 analysis was rather straightforward, ν10 exhibits obvious signs of a strong perturbation, presumably owing to interaction with the dark ν9 + ν12 state. Effective rotational constants have been derived for both the v10 = 1 and v24 = 1 states. Since only one weak, infrared active fundamental band (ν23) of trans-butadiene remains to be observed at high resolution in the far-infrared, searches for the elusive gauche conformer can now be undertaken with considerably greater confidence in the dense ro-vibrational spectrum of the trans form.

Mobility Skills With Exoskeletal-Assisted Walking in Persons With SCI: Results From a Three Center Randomized Clinical Trial.

Background: Clinical exoskeletal-assisted walking (EAW) programs for individuals with spinal cord injury (SCI) have been established, but many unknown variables remain. These include addressing staffing needs, determining the number of sessions needed to achieve a successful walking velocity milestone for ambulation, distinguishing potential achievement goals according to level of injury, and deciding the number of sessions participants need to perform in order to meet the Food and Drug Administration (FDA) criteria for personal use prescription in the home and community. The primary aim of this study was to determine the number of sessions necessary to achieve adequate EAW skills and velocity milestones, and the percentage of participants able to achieve these skills by 12 sessions and to determine the skill progression over the course of 36 sessions. Methods: A randomized clinical trial (RCT) was conducted across three sites, in persons with chronic (≥6 months) non-ambulatory SCI. Eligible participants were randomized (within site) to either the EAW arm first (Group 1), three times per week for 36 sessions, striving to be completed in 12 weeks or the usual activity arm (UA) first (Group 2), followed by a crossover to the other arm for both groups. The 10-meter walk test seconds (s) (10MWT), 6-min walk test meters (m) (6MWT), and the Timed-Up-and-Go (s) (TUG) were performed at 12, 24, and 36 sessions. To test walking performance in the exoskeletal devices, nominal velocities and distance milestones were chosen prior to study initiation, and were used for the 10MWT (≤ 40s), 6MWT (≥80m), and TUG (≤ 90s). All walking tests were performed with the exoskeletons. Results: A total of 50 participants completed 36 sessions of EAW training. At 12 sessions, 31 (62%), 35 (70%), and 36 (72%) participants achieved the 10MWT, 6MWT, and TUG milestones, respectively. By 36 sessions, 40 (80%), 41 (82%), and 42 (84%) achieved the 10MWT, 6MWT, and TUG criteria, respectively. Conclusions: It is feasible to train chronic non-ambulatory individuals with SCI in performance of EAW sufficiently to achieve reasonable mobility skill outcome milestones.

Dynamic Margins of Stability During Robot-Assisted Walking in Able-Bodied Individuals: A Preliminary Study.

Background: Gait analysis studies during robot-assisted walking have been predominantly focused on lower limb biomechanics. During robot-assisted walking, the users' interaction with the robot and their adaptations translate into altered gait mechanics. Hence, robust and objective metrics for quantifying walking performance during robot-assisted gait are especially relevant as it relates to dynamic stability. In this study, we assessed bi-planar dynamic stability margins for healthy adults during robot-assisted walking using EksoGT™, ReWalk™, and Indego® compared to independent overground walking at slow, self-selected, and fast speeds. Further, we examined the use of forearm crutches and its influence on dynamic gait stability margins. Methods: Kinematic data were collected at 60 Hz under several walking conditions with and without the robotic exoskeleton for six healthy controls. Outcome measures included (i) whole-body center of mass (CoM) and extrapolated CoM (XCoM), (ii) base of support (BoS), (iii) margin of stability (MoS) with respect to both feet and bilateral crutches. Results: Stability outcomes during exoskeleton-assisted walking at self-selected, comfortable walking speeds were significantly (p < 0.05) different compared to overground walking at self-selected speeds. Unlike overground walking, the control mechanisms for stability using these exoskeletons were not related to walking speed. MoSs were lower during the single support phase of gait, especially in the medial-lateral direction for all devices. MoSs relative to feet were significantly (p < 0.05) lower than those relative to crutches. The spatial location of crutches during exoskeleton-assisted walking pushed the whole-body CoM, during single support, beyond the lateral boundary of the lead foot, increasing the risk for falls if crutch slippage were to occur. Conclusion: Careful consideration of crutch placement is critical to ensuring that the margins of stability are always within the limits of the BoS to control stability and decrease fall risk.

Changes in bowel function following exoskeletal-assisted walking in persons with spinal cord injury: an observational pilot study.

STUDY DESIGN: Prospective, observational study. OBJECTIVE: To explore the effects of exoskeletal-assisted walking (EAW) on bowel function in persons with spinal cord injury (SCI). SETTING: Ambulatory research facility located in a tertiary care hospital. METHODS: Individuals 18-65 years of age, with thoracic vertebrae one (T1) to T11 motor-complete paraplegia of at least 12 months duration were enrolled. Pre- and post-EAW training, participants were asked to report on various aspects of their bowel function as well as on their overall quality of life (QOL) as related to their bowel function. RESULTS: Ten participants completed 25-63 sessions of EAW over a period of 12-14 weeks, one participant was lost to follow up due to early withdrawal after ten sessions. Due to the small sample size, each participant's results were presented descriptively in a case series format. At least 5/10 participants reported improvements with frequency of bowel evacuations, less time spent on bowel management per bowel day, fewer bowel accidents per month, reduced laxative and/or stool softener use, and improved overall satisfaction with their bowel program post-EAW training. Furthermore, 8/10 reported improved stool consistency and 7/10 reported improved bowel function related QOL. One participant reported worsening of bowel function post-EAW. CONCLUSION: Between 50 and 80% of the participants studied reported improvements in bowel function and/or management post-EAW training. EAW training appeared to mitigate SCI-related bowel dysfunction and the potential benefits of EAW on bowel function after SCI is worthy or further study.

Relationships between T-scores at the hip and bone mineral density at the distal femur and proximal tibia in persons with spinal cord injury.

Objective: To identify T-score values at the total hip (TH) and femoral neck (FN) that correspond to the cutoff value of <0.60 g/cm2 for heightened risk of fracture at the distal femur (DF) and proximal tibia (PT).Design: Retrospective analysis of data in a research center's database. Setting: Community-based individuals with spinal cord injury (SCI). Participants: 105 unique individuals with SCI. Outcome Measurements: DXA derived areal BMD (aBMD) and T-score of the DF, PT, TH, and FN. Results: The aBMD at the DF and PT regions were predictors of T-scores at the TH (R2 = 0.63, P < 0.001 and R2 = 0.65, P < 0.001) and FN (R2 = 0.55, P < 0.001 and R2 = 0.58, P < 0.001). Using the DF and PT aBMD of 0.60 g/cm2 as a value below which fractures were more likely to occur, the predicted T-score was -3.1 and -3.5 at the TH and -2.6 and -2.9 at the FN, respectively. However, when the predicted and observed T-score values disagree outside the 95% limit of agreement, the predicted T-score values are lower than the measured T-score values, overestimating the measured values between -2.0 and -4.0 SD. Conclusion: The DF and PT cutoff value for aBMD of 0.60 g/cm2 was a moderate predictor of T-score values at the TH and FN, with considerable inaccuracies outside the clinically acceptable limits of agreement. As such, the direct measurement of knee aBMD in persons with SCI should be performed, whenever possible, prior to prescribing weight bearing upright activities, such as robotic exoskeletal-assisted walking.

Progressive Sublesional Bone Loss Extends into the Second Decade After Spinal Cord Injury.

OBJECTIVE: The rate of areal bone mineral density (aBMD) loss at the knee (distal femur (DF) and proximal tibia ) and hip (femoral neck (FN) and total hip (TH)) was determined in persons with traumatic spinal cord injury (SCI) who were stratified into subgroups based on time since injury (TSI). DESIGN: Cross-sectional retrospective review. SETTING: Department of Veterans Affairs Medical Center and Private Rehabilitation Hospital. PARTICIPANTS: Data on 105 individuals with SCI (TSI ≤12 months, n = 19; TSI 1-5 years, n = 35; 6-10 years, n = 19; TSI 11-20 years, n = 16; TSI >20 years, n = 15) and 17 able-bodied reference (ABref) controls. INTERVENTIONS: NA Main Outcome Measures: The knee and hip aBMD values were obtained by dual energy X-ray absorptiometry (GE Lunar iDXA) using standard clinical software for the proximal femur employed in conjunction with proprietary research orthopedic knee software applications. Young-normal (T-score) and age-matched (Z-scores) standardized scores for the FN and TH were obtained using the combined GE Lunar/National Health and Nutrition Examination Survey (NHANES III) combined reference database. RESULTS: When groups were stratified and compared as epochs of TSI, significantly lower mean aBMD and reference scores were observed as TSI increased, despite similar mean ages of participants among the majority of TSI epoch subgroups. Loss in aBMD occurred at the distal femur (DF), proximal tibia (PT), FN, and TH with 46%, 49%, 32%, and 43% of the variance in loss, respectively, described by the exponential decay curves with a time to steady state (tss) occurring at 14.6, 11.3, 14, and 6.2 years, respectively, after SCI. CONCLUSIONS: Sublesional bone loss after SCI was marked and occurred as an inverse function of TSI. For aBMD at the hip and knee, tss extended into the second decade after SCI.

Rovibrational laser jet-cooled spectroscopy of SF6-rare gas complexes in the ν3 region of SF6.

High resolution infrared spectroscopy combining an external cavity quantum cascade laser with a pulsed pin hole supersonic jet is used to investigate small van der Waals (vdW) heteroclusters containing SF6 and rare gas (Rg) atoms in the ν3 region of SF6. In the first step of the analysis, the rovibrational band contours of parallel and perpendicular transitions of 1 : 1 SF6-Rg heterodimers (Rg = Ar, Kr, Xe) are simulated to derive ground and excited state parameters and hence ground state and equilibrium S-Rg distances with a precision better than 0.5 pm. These values are used to assess quantum chemistry calculations (DFT-D method) as well as semi-empirical predictions (combination rules). In the second step, the spectral signatures of the 1 : 1 heterodimers and of larger heteroclusters containing up to three Rg atoms have been identified by considering reduced vibrational red shifts, i.e., shifts normalized to the average 1 : 1 red shift. The reduced vibrational red shifts within the series of bands observed and assigned to 1 : 1 and 1 : 2 complexes are found to be independent of the Rg atom, which suggests similar 1 : 1 and 1 : 2 structures along the Rg series. In addition, the increasing number of bands when going from monomer to 1 : 2 complexes illustrates the increased lifting of vibrational degeneracy induced by Rg solvation. Finally, the vibrational shifts of the 1 : 1 SF6-Rg heterodimers are found to fit an intermolecular interaction model in which long-range attractive and short-range repulsive contributions to the vibrational shift are found to partially cancel out, the former being dominant. From the same model, well depths are obtained and are found to compare well with quantum chemistry calculations and semi-empirical combination rules.

Mechanisms for improving walking speed after longitudinal powered robotic exoskeleton training for individuals with spinal cord injury.

The goal of this study was to establish strideparameter gait models correlated to speed on individuals with chronic SCI and able-bodied controls walking with a powered robotic exoskeleton (EksoGT $^{\mathrm{ TM}}$). Longitudinal exoskeleton training $( >100$ hours) across eight individuals with SCI resulted in a 30% increase in walking speed. A simple linear regression between step length, stride length for given speed were very tightly correlated along a line of best fit $( \mathrm {p}<$.001). The temporal parameters of stride time, stance time and double support time depicted a non-linear exponentially decaying relationship for given walking speed. The research findings indicate that although longitudinal exoskeleton training reduces the temporal parameters, increases in spatial parameters are only marginal.

Multimodal cortical and subcortical exercise compared with treadmill training for spinal cord injury.

BACKGROUND AND PURPOSE: Spared fibers after spinal cord injury (SCI) tend to consist predominantly of subcortical circuits that are not under volitional (cortical) control. We aim to improve function after SCI by using targeted physical exercises designed to simultaneously stimulate cortical and spared subcortical neural circuits. METHODS: Participants with chronic motor-incomplete SCI enrolled in a single-center, prospective interventional crossover study. Participants underwent 48 sessions each of weight-supported robotic-assisted treadmill training and a novel combination of balance and fine hand exercises, in randomized order, with a 6-week washout period. Change post-intervention was measured for lower extremity motor score, soleus H-reflex facilitation; seated balance function; ambulation; spasticity; and pain. RESULTS: Only 9 of 21 enrolled participants completed both interventions. Thirteen participants completed at least one intervention. Although there were no statistically significant differences, multimodal training tended to increase short-interval H-reflex facilitation, whereas treadmill training tended to improve dynamic seated balance. DISCUSSION: The low number of participants who completed both phases of the crossover intervention limited the power of this study to detect significant effects. Other potential explanations for the lack of significant differences with multimodal training could include insufficient engagement of lower extremity motor cortex using skilled upper extremity exercises; and lack of skill transfer from upright postural stability during multimodal training to seated dynamic balance during testing. To our knowledge, this is the first published study to report seated posturography outcomes after rehabilitation interventions in individuals with SCI. CONCLUSION: In participants with chronic incomplete SCI, a novel mix of multimodal exercises incorporating balance exercises with skilled upper extremity exercises showed no benefit compared to an active control program of body weight-supported treadmill training. To improve participant retention in long-term rehabilitation studies, subsequent trials would benefit from a parallel group rather than crossover study design.

Neuromechanical adaptations during a robotic powered exoskeleton assisted walking session.

OBJECTIVE: To evaluate gait parameters and neuromuscular profiles of exoskeleton-assisted walking under Max Assist condition during a single-session for; (i) able bodied (AB) individuals walking assisted with (EXO) and without (non-EXO) a powered exoskeleton, (ii) non-ambulatory SCI individuals walking assisted with a powered exoskeleton. DESIGN: Single-session. SETTING: Motion analysis laboratory. PARTICIPANTS: Four AB individuals and four individuals with SCI. INTERVENTIONS: Powered lower extremity exoskeleton. OUTCOME MEASURES: Temporal-spatial parameters, kinematics, walking velocity and electromyography data. RESULTS: AB individuals in exoskeleton showed greater stance time and a significant reduction in walking velocity (P < 0.05) compared to non-EXO walking. Interestingly, when the AB individuals voluntarily assisted the exoskeleton movements, they walked with an increased velocity and lowered stance time to resemble that of slow walking. For SCI individuals, mean percent stance time was higher and walking velocity was lower compared to all AB walking conditions (P < 0.05). There was muscle activation in several lower limb muscles for SCI group. For AB individuals, there were similarities among EXO and non-EXO walking conditions however there were differences in several lower limb EMGs for phasing of muscle activation. CONCLUSION: The data suggests that our AB individuals experienced reduction in walking velocity and muscle activation amplitudes while walking in the exoskeleton and moreover with voluntary control there is a greater temporal-spatial response of the lower limbs. Also, there are neuromuscular phasic adaptions for both AB and SCI groups while walking in the exoskeleton that are inconsistent to non-EXO gait muscle activation.

Nuclear Spin Symmetry Conservation in 1H216O Investigated by Direct Absorption FTIR Spectroscopy of Water Vapor Cooled Down in Supersonic Expansion.

We report the results of an experimental study related to the relaxation of the nuclear spin isomers of the water molecule in a supersonic expansion. Rovibrational lines of both ortho and para spin isomers were recorded in the spectral range of H2O stretching vibrations at around 3700 cm-1 using FTIR direct absorption. Water vapor seeded in argon, helium, or oxygen or in a mixture of oxygen and argon was expanded into vacuum through a slit nozzle. The water vapor partial pressure in the mixture varied over a wide range from 1.5 to 102.7 hPa, corresponding to a water molar fraction varying between 0.2 and 6.5%. Depending on expansion conditions, the effect of water vapor clustering was clearly seen in some of our measured spectra. The Boltzmann plot of the line intensities allowed the H2O rotational temperatures in the isentropic core and in the lateral shear layer probed zones of the planar expansion to be determined. The study of the OPR, i.e., the ratio of the ortho to para absorption line intensities as a function of Trot, did not reveal any signs of the OPR being relaxed to the sample temperature. In contrast, the OPR was always conserved according to the stagnation reservoir equilibrium temperature. The conservation of the OPR was found irrespective of whether water molecule clustering was pronounced or not. Also, no effect of the paramagnetic oxygen admixture enhancing OPR relaxation was observed.

Conformational landscape of the SF6 dimer as revealed by high resolution infrared spectroscopy and complexation with rare gas atoms.

Taking advantage of a versatile set-up, combining pulsed pin hole or slit nozzle supersonic expansion with an external cavity quantum cascade laser, the rovibrational absorption spectrum of the SF6 dimer in the ν3 mode region has been revisited at high resolution under various experimental conditions in SF6:He mixtures. Two new rotationally resolved spectral bands have been identified in the range of the parallel band of the dimer spectrum in addition to that previously reported. Among these three spectral features, two of them are assigned to conformations of the dimer (noted #1 and #2), clearly distinguished from their different S-S interatomic distances, i.e. 474 and 480 pm respectively. The third one is assigned to a (SF6)2-He complex, from comparison with additional experiments in which (SF6)2-Rg heterotrimers (Rg = Ne, Ar, Kr, Xe) are observed. A schematic picture of the potential energy landscape of the SF6 dimer in terms of a nearly flat surface is proposed to account for the conformational relaxation observed in the expansions and for the structure of the (SF6)2-Rg heterotrimers, which are exclusively formed from the conformer #2 dimer. Although modelling qualitatively supports this picture, much effort has still to be achieved from a theoretical point of view to reach a quantitative agreement with the present benchmark experimental data both in terms of structure and energetics.

Characterising molecules for fundamental physics: an accurate spectroscopic model of methyltrioxorhenium derived from new infrared and millimetre-wave measurements.

Precise spectroscopic analysis of polyatomic molecules enables many striking advances in physical chemistry and fundamental physics. We use several new high-resolution spectroscopic devices to improve our understanding of the rotational and rovibrational structure of methyltrioxorhenium (MTO), the achiral parent of a family of large oxorhenium compounds that are ideal candidate species for a planned measurement of parity violation in chiral molecules. Using millimetre-wave and infrared spectroscopy in a pulsed supersonic jet, a cryogenic buffer gas cell, and room temperature absorption cells, we probe the ground state and the Re[double bond, length as m-dash]O antisymmetric and symmetric stretching excited states of both CH3187ReO3 and CH3185ReO3 isotopologues in the gas phase with unprecedented precision. By extending the rotational spectra to the 150-300 GHz range, we characterize the ground state rotational and hyperfine structure up to J = 43 and K = 41, resulting in refinements to the rotational, quartic and hyperfine parameters, and the determination of sextic parameters and a centrifugal distortion correction to the quadrupolar hyperfine constant. We obtain rovibrational data for temperatures between 6 and 300 K in the 970-1015 cm-1 range, at resolutions down to 8 MHz and accuracies of 30 MHz. We use these data to determine more precise excited-state rotational, Coriolis and quartic parameters, as well as the ground-state centrifugal distortion parameter DK of the 187Re isotopologue. We also account for hyperfine structure in the rovibrational transitions and hence determine the upper state rhenium atom quadrupole coupling constant eQq'.