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Individuals with anterior cruciate ligament reconstruction (ACLR) exhibit less knee kinematic variability while walking than uninjured controls, associated with deleterious changes in cartilage composition linked to an increased risk for early knee osteoarthritis (KOA). It is unknown whether less knee kinematic variability is also associated with worse knee-related patient-reported outcomes (PROs) consistent with KOA development. This study examined associations between kinematic variability during gait and PROs in individuals post-ACLR. Gait kinematics and the Knee Injury and Osteoarthritis Outcome Score (KOOS) were collected from 45 participants 6-months post-ACLR (67% Females; 21.45 ± 4.56 years). Overground gait biomechanics using 3D motion capture were collected, and knee kinematics were extracted for post-processing. Sample entropy (SampEn) was used to calculate knee kinematic variability. Pearson's product-moment correlations were conducted to determine the associations between SampEn and KOOS sub-scores. Additionally, independent samples t-tests were performed to evaluate potential differences in SampEn outcomes between individuals with and without clinically relevant symptoms (defined in the introduction). Less sagittal plane kinematic variability is associated with greater pain (r = 0.37, p = 0.01) and symptoms (r = 0.32, p = 0.03). Symptomatic participants demonstrated less sagittal plane knee kinematic variability compared to asymptomatic participants (p = 0.01). The findings suggest less variable gait patterns 6-months post-ACLR may be linked to KOA-related symptoms. [ABSTRACT FROM AUTHOR]

Purpose: Strong observational evidence has linked changes in limb loading during walking following anterior cruciate ligament reconstruction (ACLR) to posttraumatic osteoarthritis (PTOA). It remains unknown if manipulating peak loading influences joint tissue biochemistry. Thus, the purpose of this study is to determine whether manipulating peak vertical ground reaction force (vGRF) during gait influences changes in serum cartilage oligomeric matrix protein (sCOMP) concentrations in ACLR participants. Methods: Forty ACLR individuals participated in this randomized crossover study (48% female, age = 21.0 ± 4.4 years, BMI = 24.6 ± 3.1). Participants attended four sessions, wherein they completed one of four biofeedback conditions (habitual loading (no biofeedback), high loading (5% increase in vGRF), low loading (5% decrease in vGRF), and symmetrical loading (between-limb symmetry in vGRF)) while walking on a treadmill for 3000 steps. Serum was collected before (baseline), immediately (acute post), 1 h (1 h post), and 3.5 h (3.5 h post) following each condition. A comprehensive general linear mixed model was constructed to address the differences in sCOMP across all conditions and timepoints in all participants and a subgroup of sCOMP Increasers. Results: No sCOMP differences were found across the entire cohort. In the sCOMP Increasers, a significant time × condition interaction was found (F9,206 = 2.6, p = 0.009). sCOMP was lower during high loading than low loading (p = 0.009) acutely (acute post). At 3.5 h post, sCOMP was higher during habitual loading than symmetrical loading (p = 0.001). Conclusion: These data suggest that manipulating lower limb loading in ACLR patients who habitually exhibit an acute increase in sCOMP following walking results in improved biochemical changes linked to cartilage health. Key Points • This study assesses the mechanistic link between lower limb load modification and joint tissue biochemistry at acute and delayed timepoints. • Real-time biofeedback provides a paradigm to experimentally assess the mechanistic link between loading and serum biomarkers. • Manipulating peak loading during gait resulted in a metabolic effect of lower sCOMP concentrations in a subgroup of ACLR individuals. • Peak loading modifications may provide an intervention strategy to mitigate the development of PTOA following ACLR. [ABSTRACT FROM AUTHOR]

Introduction: Aberrant gait variability has been observed after anterior cruciate ligament reconstruction (ACLR), yet it remains unknown if gait variability is associated with early changes in cartilage composition linked to osteoarthritis development. Our purpose was to determine the association between femoral articular cartilage T1ρ magnetic resonance imaging relaxation times and gait variability. Methods: T1ρ magnetic resonance imaging and gait kinematics were collected in 22 ACLR participants (13 women; 21 ± 4 yr old; 7.52 ± 1.43 months post-ACLR). Femoral articular cartilage from the ACLR and uninjured limbs were segmented into anterior, central, and posterior regions from the weight-bearing portions of the medial and lateral condyles. Mean T1ρ relaxation times were extracted fromeach region and interlimb ratios (ILR) were calculated (i.e.,ACLR/uninjured limb). Greater T1ρ ILR values were interpreted as less proteoglycan density (worse cartilage composition) in the injured limb compared with the uninjured limb. Knee kinematics were collected at a self-selected comfortable walking speed on a treadmill with an eight-camera three-dimensional motion capture system. Frontal and sagittal plane kinematics were extracted, and sample entropy was used to calculate kinematic variability structure (KVstructure). Pearson's product-moment correlations were conducted to determine the associations between T1ρ and KVstructure variables. Results: Lesser frontal plane KVstructure was associated with greater mean T1ρ ILR in the anterior lateral (r = -0.44, P = 0.04) and anterior medial condyles (r = -0.47, P = 0.03). Lesser sagittal plane KVstructure was associated with greater mean T1ρ ILR in the anterior lateral condyle (r = -0.47, P = 0.03). Conclusions: The association between less KVstructure and worse femoral articular cartilage proteoglycan density suggests a link between less variable knee kinematics and deleterious changes joint tissue changes. The findings suggest that less knee kinematic variability structure is a mechanism linking aberrant gait to early osteoarthritis development. [ABSTRACT FROM AUTHOR]

For persons with multiple sclerosis (MS), the general decline in neuromuscular function underlies diminished balance, impaired gait and consequently, increased risk of falling. During gait, optimal control of head motion is an important feature which is achieved partly through control of the trunk-neck region to dampen gait-related oscillations. The primary aim of this study was to examine the effect performing a 6-minute walk test (6MWT) has on head, neck and trunk accelerations in individuals with MS. This was addressed using a repeated measures generalized linear model. We were also interested in assessing whether the 6MWT has an impact on a person's falls risk and specific physiological measures related to falls. Finally the relation between the amplitude (i.e., mean RMS) of head and trunk accelerations and falls risk was examined using linear regression. The main results were that over the course of the 6MWT, individuals progressively slowed down coupled with a concurrent increase in gait-related upper body accelerations (p's > 0.05). Despite the increased acceleration, no significant changes in attenuation from the trunk to the head were observed, indicating that persons were able to maintain an optimal level of control over these oscillations. Performing the 6MWT also had a negative impact on posture, with falls risk significantly increasing following this test (p > 0.05). Interestingly, the overall falls risk values were strongly linked with vertical accelerations about the trunk and head, but not average walking speed during the 6MWT. Overall, performing the 6MWT leads to changes in walking speed, upper body acceleration patterns and increases in overall falls risk. [ABSTRACT FROM AUTHOR]

Biofeedback has been effectively implemented to improve the mediation and distribution of joint loads during gait, however, the inability to effectively coordinate lower limb movement by altering loading patterns may increase pathological stress and risk of injury and deleterious joint changes. This study examined the influence cueing an increase or decrease in lower extremity loading has on inter- and intralimb joint coordination during gait, applied herein for 12 persons following anterior cruciate ligament reconstruction across three loading conditions (control, high, and low). Visual biofeedback was presented on a screen via a force-measuring treadmill with targeted changes prescribed based on stride-to-stride peak vertical ground reaction forces bilaterally. The pattern and stability of coordination dynamics among each of the ankle, hip and knee joint pairs were assessed via discrete relative phase and cross-recurrence quantification analyses for each condition. High and low loading altered the pattern and stability of intralimb coordination; low loading led to decreased coordination stability (20° greater than control condition) and high loading resulted in a more tightly coupled coordination pattern (higher %CDET). With thoughtful consideration for movement control, biofeedback can be used to target mechanisms leading to long-term deleterious joint adaptations. [ABSTRACT FROM AUTHOR]

Autism spectrum disorder (ASD) is a complex diagnosis characterized primarily by persistent deficits in social communication/interaction and repetitive behavior patterns, interests, and/or activities. ASD is also characterized by various physiological and/or behavioral features that span sensory, neurological, and neuromotor function. Although problems with lower body coordination and control have been noted, little prior research has examined lower extremity strength and proprioception, a process requiring integration of sensorimotor information to locate body/limbs in space. We designed this study to compare lower limb proprioception and strength in adolescents with ASD and neurotypical controls. Adolescents diagnosed with ASD (n = 17) and matched controls (n = 17) performed ankle plantarflexion/dorsiflexion bilateral proprioception and strength tests on an isokinetic dynamometer. We assessed position-based proprioception using three targeted positions (5 and 20-degrees plantarflexion and 10-degrees dorsiflexion) and speed-based proprioception using two targeted speeds (60 and 120-degrees/second). We assessed strength at 60-degrees/second. Participants with ASD performed 1.3-times more poorly during plantarflexion position and 2-times more poorly during the speed-based proprioception tests compared to controls. Participants with ASD also exhibited a 40% reduction in plantarflexion strength compared to controls. These findings provide insight into mechanisms that underly the reduced coordination, aberrant gait mechanics, and coordination problems often seen in individuals with ASD, and the identification of these mechanisms now permits better targeting of rehabilitative goals in treatment programs. [ABSTRACT FROM AUTHOR]

Background: The development of stable postural control is characterized by changes in sway variability and periods of rapid reorganization of motor system components.Research Question: The current study examined whether changing biomechanical and perceptual demands influences the postural control behavior during development.Method: The center of pressure (COP) was assessed via a cross-sectional design. Data were collected from 48 females in three age groups (late childhood, mid-adolescence, and young adulthood) during four quiet stance conditions: (1) eyes open with feet apart, (2) eyes open with feet together, (3) eyes closed with feet apart, and (4) eyes closed with feet together. Linear measures included total path length of the COP and the mean/standard deviation of the overall COP position and speed. To characterize the sway patterns via nonlinear analyses, the speed and two-dimensional positional time series were submitted to sample entropy and Renyi entropy, respectively.Results: The linear results indicated that the late childhood group displayed longer COP trajectories (p < .001) and faster and more variable COP speed (p's < .001). These results held for both the feet apart and feet together conditions, independent of vision. The nonlinear results indicated that the late childhood group exhibited less regularity, overall, in their COP sway position (i.e., Renyi entropy) compared to the two older groups in the feet apart condition (p's ≤ .041), and to the young adults in the feet together condition, independent of vision (p <  .001). However, the mid-adolescent group demonstrated greater regularity in their COP speed (i.e., sample entropy) when their eyes were closed compared to the other two groups, independent of stance (p's < .05).Significance: The linear results support previous findings, while the nonlinear measures indicate sway characteristics that may provide a window into the development of underlying control processes that regulate quiet standing. [ABSTRACT FROM AUTHOR]

Purpose: Dental hygienists perform precision instrumentation tasks repetitively throughout the workday, placing them at increased risk for developing a musculoskeletal disorder. The purpose of this pilot study was to determine differences in muscle activity and pinch force generation between the traditional scaling technique and a modified scaling technique. Methods: A convenience sample of dental hygienists (n=12) acted as their own controls in this counterbalance-designed pilot study. Muscle activity and pinch forces were assessed while participants performed traditional and modified scaling techniques with designated instruments on artificial calculus applied to the lower left quadrant of a typodont, for a period of five minutes. Surface electromyography was used to measure muscle activity; sensors attached to the instrument handle measured pinch forces. Participants were surveyed regarding the instruments used and scaling technique preferences at the conclusion of the session. Parametric and non-parametric tests were used to analyze the data. Descriptive statistics were used to analyze the exit survey. Results: The modified scaling technique required less muscle activity than the traditional technique while scaling, however results were not significant (p>0.05). The traditional scaling technique required greater overall pinch force during scaling (p=.00). Pairwise comparisons revealed significant differences between pinch force generation in the thumb for the two scaling techniques (Z = -2.401, p= 0.016) and in the index finger (Z = -2.223, p= 0.026). The traditional scaling technique generated more pinch force (thumb x=7.25±4.99, index finger x=2.86±2.14) when compared to the modified scaling technique (thumb x=4.52±2.32, index finger x=1.65±1.28). Participants had a slightly higher preference for the instrument utilized for the modified scaling technique in terms of balance, maneuverability, overall comfort and the associated scaling technique as compared to the instrument utilized for the traditional scaling technique. Conclusion: Use of a modified scaling technique may reduce muscle activity and pinch force generation as compared to the traditional lateral pressure scaling technique during instrumentation. Future research on ergonomic scaling techniques is needed to determine their efficacy and impact on musculoskeletal disorders. [ABSTRACT FROM AUTHOR]

Introduction: To determine whether individuals with a history of anterior cruciate ligament reconstruction (ACLR) exhibit altered neuromotor function compared to healthy controls. It was hypothesized that the ACLR group would have slower postural responses compared to healthy individuals of similar age. Materials and Methods: Sixteen adults with a unilateral ACLR and 16 matched healthy controls participated. General assessments of neuromotor function were gathered and included measures of reaction time (both seated and postural conditions), walking ability, balance, ankle ROM, proprioception, knee joint laxity, patellar tendon reflex latency, and quadriceps strength. Data were analyzed using mixed generalized linear models with between‐subject (ie, controls, ACLR) and within‐subject factors (ie, affected, unaffected limb). Results: Individuals with an ACLR exhibited a significant slowing of their postural reaction times compared to the control individuals. The ACLR group was slower under both the simple (ACLR: 484 ± 6.17 ms, control: 399 ± 1.95 ms) and choice reaction time conditions (ACLR: 550 ± 43 ms, control: 445 ± 43 ms). No other group differences were found in any of the other measures. Conclusion: Overall, ACLR individuals had a reduced ability to respond quickly under more challenging postural conditions (ie, stepping response). This finding would indicate that the impact of an ACLR is not purely mechanical and restricted to the joint. Rather, injury and reconstruction of the ACL impact neural mechanisms, altering individuals' ability to respond under challenging balance tasks. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study was to determine strength of muscles involved with instrumentation (scaling) by dental hygienists and the additive effects of cellular (mobile) phone usage, as indicated by measurements of muscular force generation. Methods: A convenience sample of licensed dental hygienists currently in clinical practice (n=16) and an equal number of individuals not currently using devices/tools repetitively for work (n=16), agreed to participate in this pilot study. All participants completed a modified cell phone usage questionnaire to determine their use pattern and frequency. Upon completion of the questionnaire, participants' force production in six muscle groups was measured using a hand-held dynamometer. Descriptive statistics were used to analyze the data. Results: A total of 16 licensed dental hygienists (n=16) and 16 participants with no history of using tools/devices repetitively for work (n=16), comprised the experimental and control groups, repectively. The control group generated greater muscle force than the experimental group for the abductor pollicis longus (p=0.045). Significant differences were identified when comparing the low mobile phone users in the experimental group to the control group for the flexor pollicis brevis (p=0.031), abductor pollicis longus (p=0.031), and flexor digitorum (p=0.006), with the control group demonstrating higher muscle force. Years in clinical practice and mobile phone use was shown to have a significant effect on muscular force generation for the flexor pollicis brevis (F=3.645, df=3, p=0.020) and flexor digitorum (F=3.560, df=3, p=0.022); subjects who practiced dental hygiene the longest produced the least amount of muscle force. Conclusion: Results from this pilot study indicate there are no significant additive effects of cell phone use and dental hygiene practice on finger muscles used for instrumentation. However, results indicate that dental hygiene practice demonstrated significant effects on muscular strength as compared to individuals who do not use tools/devices repetitively for work. The small sample size may have impacted results and the study should be repeated with a larger sample. [ABSTRACT FROM AUTHOR]

Individuals with autism spectrum disorder (ASD) can exhibit a range of movement issues, which are often characterized by a general slowing of movement responses that can extend to walking speed. The current study was designed to examine the spatio-temporal features and pattern of acceleration for the trunk, neck and head during walking for a cohort of adults with ASD compared to neurotypical individuals. Twenty young adults with ASD and 20 age-matched neurotypical adults participated in this study. Participants performed five walking trials across a 20ft Protokinetics pressure sensitive surface at their preferred walking speed. Accelerations were collected using three triaxial accelerometers affixed to the head, neck, and lower trunk. Comparisons of acceleration amplitude (i.e., RMS), frequency, segmental gain and regularity (i.e., SampEn) during the walking tasks were performed. Results revealed that the adults with ASD walked slower than the neurotypical persons with a greater proportion of time spent in double stance. Despite walking at a slower pace overall, the adults with ASD exhibited a decreased ability to attenuate gait-related oscillations from the trunk to the head. Overall, these findings suggest that adults with ASD exhibited a decreased ability to accommodate and dampen those accelerations related to walking. As declines in gait speed are often linked with loss of head control, one suggestion is that the inability to appropriately compensate for gait-related oscillations may, in part, explain why persons with ASD walk slower. [ABSTRACT FROM AUTHOR]

Background The study was designed to examine coordination differences in walking between individuals with an anterior cruciate ligament reconstruction compared with healthy matched controls. Predictions from the extended Haken, Kelso, and Bunz coupled oscillator model were tested in these populations. Methods Seventeen persons with anterior cruciate ligament reconstruction and 17 matched controls participated in the study. Sagittal plane angular knee displacement was recorded using electrogoniometers over the lateral right and left knee joints while participants walked at five walking speeds overground. Coordination pattern and stability between the knees were quantified by mean and standard deviation of relative phase, respectively. Findings Mean relative phase was not influenced by walking speed or group. For both groups, coordination stability was maximal when individual's walked at their preferred gait speed. However, the anterior cruciate ligament reconstruction group demonstrated reduced coordination stability compared with healthy controls across the five speeds. Multiple regression analyses found that people with anterior cruciate ligament reconstruction who deviated more from antiphase coordination had decreased coordination stability. Interpretation Anterior cruciate ligament reconstruction results in decreased coordination stability, indicative of reduced coupling strength between the legs. This change in gait coordination, which has not previously been found in the literature, may contribute to the increased rate of re-injury and degeneration in individuals who have had this reconstructive surgery. Application of a motor control model enhances our understanding of the influence of an injury on coordination during gait. [ABSTRACT FROM AUTHOR]

Context: A comprehensive systematic review of the literature on the use of augmented information in anterior cruciate ligament (ACL) injury-prevention programs to improve jumplanding technique was conducted. The use of motor-learning concepts could provide more robust means of preventing ACL injuries. Objective: To systematically summarize the effectiveness of augmented information in improving the biomechanical factors associated with an increased risk for ACL injury. Data Sources: Articles were retrieved using the electronic databases of PubMed, MEDLINE, CINAHL, and Google Scholar and 3 lines of truncated search words: (a) lower extremity, knee, ACL, and anterior cruciate ligament; (b) prevention, injury prevention, and prehab; and (c) augmented information, augmented feedback, feedback, cue, and instruction. We also performed a hand search of the reference lists of the screened articles. Data Extraction: We independently assessed the methodologic quality using the Cochrane Group on Screening and Diagnostic Test Methods list. Articles were placed in 1 of 3 augmented-information categories: prescriptive, feedback, or transition. Articles were also categorized based on whether the information likely encouraged an internal or external focus of attention. Data Synthesis: The searches identified a total of 353 studies, of which 18 were included. Most researchers found that augmented information could lead to technique changes to reduce the biomechanical risk factors associated with ACL injury. The average methodologic quality of the studies was 11.8 out of 17, with a range from 8 to 15. The authors of only 7 studies examined retention of the improved techniques. Conclusions: The evidence suggests that augmented information can be used to significantly improve the biomechanical indicators associated with ACL injury and to enhance current ACL injury-prevention programs. Combined prescriptive and feedback information that encouraged both internal and external foci led to the largest retention effect sizes. [ABSTRACT FROM AUTHOR]

Autism spectrum disorder (ASD) is a common neurodevelopmental disorder, whose core symptom domains include impaired social communication and narrowed interests and/or repetitive behaviors; in addition, deficits of general cognition, neuromotor function, and movement ability can be observed. This study was designed to examine differences in neuromotor and cognitive functions for a group of young adults with ASD and age-matched controls. It was also of interest to assess whether changes in the intra-individual variability (IIV) of these selected neuromotor and cognitive tasks also occurred. Increased IIV in persons with ASD may reveal important organizational features of their neuromotor system that differ from neurotypical controls. Twenty neurotypical adult individuals (24.3 ± 2.8 years) and twenty adults with a clinician-assigned diagnosis of ASD (21.2 ± 4.4 years) participated in this study. Specific cognitive and motor assessments included Trails Making Tests A&B, Symbol Digit Modalities Test, Purdue Pegboard Test, simple reaction time, finger tapping, hand grip strength, balance, and gait. Results revealed that the ASD adults exhibited decreased upper limb strength and slower responses for finger tapping, hand dexterity, reaction times, and gait compared to the non-ASD controls. The general slowing of motor responses for the persons with ASD was also associated with increased within-subject variability during the reaction time, finger tapping, hand grip, and gait assessments compared to neurotypical adults, illustrating that IIV measures may be a useful marker of widespread neuromotor dysfunction for adults with ASD. Overall, these findings are consistent with clinical observations that abnormalities of movement performance and cognitive performance are an associated feature of ASD in young adults. [ABSTRACT FROM AUTHOR]

This study was designed to assess and compare the pattern of acceleration from the lower trunk, neck and head regions for individuals with reconstructed ACL compared to healthy controls during walking. Participants with unilateral ACL reconstruction and matched control persons participated in the study. Accelerations were collected using three triaxial accelerometers attached to the head, neck, and lower trunk. Measures of amplitude and signal regularity of the acceleration data were performed. Similarities were seen between both groups with regards to the general acceleration patterns in all three axes. However, the results also revealed that the individuals with ACL reconstruction had significantly greater peak power in the AP direction at higher frequencies, indicating a reduced ability to attenuate frequency signals. Further, the ACL group had a reduced ability to control head motion during gait, as indicated by reduced regularity in VT. Both groups demonstrated a similar pattern of gait-related oscillations across the head, neck and trunk segments. However, adults with a reconstructed ACL demonstrated a reduced capacity to compensate for the higher frequency components of the gait signal, which may have led to a decline in head control. Overall, these findings indicate that previous damage to the ACL is not simply localized to the knee joint, but influences upper body control, too. [ABSTRACT FROM AUTHOR]

The purpose of this study was to assess the effectiveness of an eight-week surfing intervention for 16 children with disabilities. The assessment procedure consisted of pre and post physical fitness measures to determine the benefits of this intervention. Our results showed an overall improvement in upper body strength (right: P = 0.024, left: P = 0.022), core strength (P = 0.002) and cardiorespiratory endurance (P = 0.013). This research is the first of its kind, illustrating the feasibility and effectiveness of a surfing intervention on improving the physical fitness of children with disabilities. [ABSTRACT FROM AUTHOR]

Purpose The objective of this study was to compare the effects of ten commercially available instrument handle designs' mass and diameter on forearm muscle activity during a simulated periodontal scaling experience. Methods A convenience sample of 25 registered dental hygienists were recruited for this IRB-approved study. Ten commercially available instruments were categorized into four groups based on their masses and diameters: large diameter/light mass, small diameter/light mass, large diameter/heavy mass, and small diameter/heavy mass. Participants were randomized to four instruments with one from each group. Participants scaled with each instrument in a simulated oral environment while muscle activity was collected using surface electromyography. Muscle activity was compared among the four instrument group types. Results Muscle activity of the flexor digitorum superficialis was not significantly influenced by instrument mass (p=0.60) or diameter (p=0.15). Flexor pollicis longus muscle activity was not significantly influenced by instrument mass (p=0.81); diameter had a significant effect (p=0.001) with smaller diameter instruments producing more muscle activity. For the extensor digitorum communis and extensor carpi radialis brevis, instrument mass did not significantly affect muscle activity (p=0.64, p=0.43), while diameter narrowly failed to reach significance for both muscles (p=0.08, p=0.08); muscle activity for both muscles increased with smaller diameter instruments. Conclusion Results from this study indicate instrument diameter is more influential than mass on muscle activity generation; small diameter instruments increased muscle activity generation when compared to large diameter instruments. Future research in real-world settings is needed to determine the clinical impact of these findings. [ABSTRACT FROM AUTHOR]

There is a growing interest in the bacterial pellicle, a biofilm floating at the air-liquid interface. Pellicles have been well studied in the Gram-positive bacterium B acillus subtilis, but far less in Gram-negative bacteria, where pellicle studies have mostly focused on matrix components rather than on the regulatory cascades involved. Several Gram-negative bacteria, including pathogenic bacteria, have been shown to be able to form a pellicle under static conditions. Here, we summarize the growing body of knowledge about pellicle formation in Gram-negative bacteria, especially about the components of the pellicle matrix. We also propose that the pellicle is a specific biofilm, and that its formation involves particular processes. Since this lifestyle concerns a growing number of bacteria, its properties undoubtedly deserve further investigation. [ABSTRACT FROM AUTHOR]

Educational aquatic programming offers necessary physical activity opportunities to children with disabilities and the benefits of aquatic activities are more pronounced for children with disabilities than for their able-bodied peers. Similar benefits could potentially be derived from surfing in the ocean. This article describes an adapted surfing program that was designed to develop and enhance the children's strength, flexibility, range of motion, coordination, balance, and psychosocial development. Throughout the program, the children and their surf instructors were encouraged to set realistic individual goals. Many positive outcomes were derived from the project, including gains in social development and self-confidence. [ABSTRACT FROM AUTHOR]

Floating biofilm, or pellicle, is a biofilm found at the air-liquid interface. Here, we show that pellicle development of the aquatic bacterium Shewanella oneidensis is under the control of the chemotaxis system ( Che3), a regulatory system known to pilot planktonic cell motion according to environmental cues. Deletion of the histidine kinase cheA3 or the response regulator cheY3 gene led to a heterogeneous pellicle or to the absence of pellicle respectively. In addition, a non-phosphorylatable CheY3- D56A mutant was unable to promote pellicle formation. Kinetic analysis revealed that pellicle formation occurs in three steps: rapid formation of a thin pellicle evolving into a heterogeneous biofilm and finally into a thick homogeneous biofilm. Depletion of oxygen not only abolished initiation of pellicle formation but also blocked pellicle maturation. This study thus demonstrates an essential role of aerotaxis (chemotaxis towards oxygen) in floating biofilm development in S. oneidensis, and it also reveals that pellicle formation is a step-by-step process. [ABSTRACT FROM AUTHOR]

Highlights: [•] cagPAI, oipA, vacA, bab genes microevolution phenomenon was investigated. [•] Analysis of jhp0926, jhp0940, jhp0945, jhp0947 and jhp0949 was also included. [•] A significantly higher number of variants of a single strain was found in patients with gastritis. [•] In patients with peptic ulcer disease, the selection of a particular variant may occur. [•] In patients with gastritis the same variant co-exists with other. [Copyright &y& Elsevier]

Abstract: Bacteria, and in particular marine bacteria, can be found in environments that are poor in nutrients. To survive, they are able to move toward more favorable niches by a mechanism called chemotaxis, whose first step consists in the detection of substrates by chemoreceptors. We developed a chemotactic assay enabling rapid testing of several hundred different solutes and we identified several molecules eliciting a chemotactic response from two aquatic Shewanella species. We propose that this assay be used for other bacteria to determine the repertoire of chemotactic molecules, generally not clearly elucidated. [Copyright &y& Elsevier]

A 70 keV 40 A hydrogen beam injector has been developed at Cadarache for a plasma diagnostic [motional Stark effect (MSE)] to provide a measurement of the plasma current distribution in the Tore-Supra tokamak. We present in this article the principle and the first experimental results of the injector, where a new type, and advantageous, energy recovery system, based on a magnetic neutralizer plasma confinement, has been developed. The hydrogen ion beam is accelerated to 70 keV with a three-grid multiaperture system (aperture diameter φ = 11 mm) with an ion current density of ≈ 160 mA/cm². An ion source with a shape (height 1.2 m, width 80 mm) specifically adapted to the recovery system has been developed to meet the injector requirements: uniformity, high proton fraction (>80%), and high current density, ≈160 mA/cm² over the whole extraction surface (900 cm²). A neutral (H[sup 0]) beam power of 500 kW has been achieved with a divergence of ≈0.6º at 70 keV. [ABSTRACT FROM AUTHOR]

While 3D motion capture (MoCap) has enabled the high-resolution analysis of human movement, major limiting factors of these systems are their high cost and restriction to laboratory settings. This limits the generalizability of data captured in a controlled environment to movements performed during sport. The development of algorithms to support portable markerless MoCap systems provide a low-cost functional alternative to measure kinematics during sport-specific movement tasks in a real-world setting, with minimal invasiveness. PURPOSE: Assess the accuracy of a custom, portable, and markerless MoCap system in capturing lower limb joint kinematics during functional motor tasks compared to a gold-standard 3D MoCap system. METHODS: 15 subjects (12 females; age: 20±1 year) performed three motor tasks (8 trials each): walking, running, and cutting in a laboratory. The portable MoCap system comprised of 5 high-definition 2D cameras and proprietary pose-estimation software (wrnchAI ver 1.2.2) to capture lower limb landmark points and establish joint positions. Subjects were outfitted with 29 retroreflective markers for concurrent capture via a 10-camera Vicon 3D MoCap system. We extracted bilateral summary variables of ankle, knee, and hip angles in the sagittal and frontal planes. To assess the agreement between systems, coefficient of multiple determination (R²), root mean squared error (RMSE), and mean joint angle estimation error (MEE) were calculated per trial. RESULTS: R² values revealed a strong relationship (range: 0.64-0.94). RMSE and MEE results indicate a strong to moderate accuracy (RMSE range: 0.83°- 8.15°, MEE range: 0.86° - 9.40°). See Table 1 for summary of results. CONCLUSION: The findings indicate the portable MoCap system with wrnchAI software effectively captured lower limb kinematics during functional motor tasks. Overall, portable MoCap technology can provide a cost-effective tool to assess athletes in a natural sport environment. [ABSTRACT FROM AUTHOR]

PURPOSE: New methods are needed to identify those at risk of developing posttraumatic osteoarthritis (PTOA). We employed a novel eXplainable machine learning (X-ML) approach to predict PTOA-related symptoms and identify differentiating markers post-anterior cruciate ligament reconstruction (ACLR) via serum biomarkers and patient demographics. METHODS: Serum was analyzed from 45 patients (26 F, 19 M; 21.27 ± 3.98 years; 23.93 ± 2.43 body mass index [BMI]) within 15 days of ACL injury. Age, sex, BMI, monocyte chemoattractant protein-1 (MCP-1), matrix metalloproteinase-3 (MMP-3), cartilage oligomeric matrix protein (COMP), and type-II collagen breakdown (C2C), synthesis (CPII) and turnover (C2C:CPII) were input to train X-ML models to predict PTOA symptoms 12 months post-ACLR, as previously defined by Knee Injury and Osteoarthritis Outcome Score cut-offs. Four separate genetic algorithm-based fuzzy X-ML models were trained via 80-20 training (n = 36) and hold-out validation (n = 9) stratified re-sampled splits, to classify dominant membership in one of two output functions (i.e., symptomatic vs. no symptoms). Model performance indices were computed, with exemplar human-readable rules defined by dominant mappings of inputs to one of three membership functions (i.e., low, moderate and high). RESULTS: See Table 1 for model performance indices. Exemplar rule comparison of two female patients--correctly classified as "symptomatic" and "no symptoms"--from the same validation set indicated higher COMP, and moderately higher C2C and C2C:CPII as differentiators for "symptomatic" classification. CONCLUSIONS: X-ML modeling is able to predict PTOA-related symptoms 12 months post-ACLR via higher serum COMP and type-II collagen turnover biomarkers. They also illustrate the unique capability of X-ML to provide human-readable insights, which is an important first step for proactive identification of individuals at higher risk of PTOA symptoms post-ACLR. [ABSTRACT FROM AUTHOR]

Biofeedback has recently been explored to target deviant lower extremity loading mechanics following anterior cruciate ligament reconstruction (ACLR) to mitigate the development of post traumatic osteoarthritis. The impact this feedback has on the structure of the stride interval dynamics-a barometer of gait system health-however, have yet to be examined. This study was designed to assess how feedback, used to alter lower-extremity loading during gait, affects the structure of stride interval variability by examining long-range stride-to-stride correlations during gait in those with unilateral ACLR. Twelve participants walked under three separate loading conditions: (1) control (i.e., no cue) (2) high loading, and (3) low loading. Baseline vertical ground reaction force (vGRF) data was used to calculate a target 5% change in vGRF for the appropriate loading condition (i.e., high loading was +5% vGRF, low loading was -5% vGRF). The target for the load condition was displayed on a screen along with real-time vGRF values, prescribing changes in stride-to-stride peak vertical ground reaction forces of each limb. From time-series of stride intervals (i.e., duration), we analyzed the mean and standard deviation of stride-to-stride variability and, via detrended fluctuation analysis (i.e., DFA α), temporal persistence for each feedback condition. Both the high and low loading conditions exhibited a change toward more temporally persistent stride intervals (high loading: α =0.92, low loading: α = 0.98) than walking under the control condition (α = 0.78; high vs. control: p = .026, low vs. control: p = .001). Overall, these results indicate that altering lower extremity load changes the temporal persistence of the stride internal dynamics in ACLR individuals, demonstrating the implications of the design of gait training interventions and the influence feedback has on movement strategies. [ABSTRACT FROM AUTHOR]

Lesser peak vertical ground reaction force (vGRF) has been widely reported among individuals with anterior cruciate ligament reconstruction (ACLR). Peak vGRF remains less than uninjured controls and relatively stable during the first year following ACLR. However, it is unknown whether there are subgroups of individuals exhibiting consistently greater peak vGRF in the first 6‐months following ACLR and if individuals with consistently greater peak vGRF exhibit kinematic and kinetic gait differences compared to individuals with low vGRF. The purpose of this study was to determine if distinct clusters exist based upon magnitude of peak vGRF 2‐ and 6‐months post‐ACLR. Subsequently, we explored between cluster differences in vGRF, knee flexion angle, and sagittal and frontal plane knee kinetics throughout stance between clusters. Forty‐three individuals (58.1%female, 21.4 ± 4.4 years‐old, 95.3% patellar‐tendon autograft) completed five gait trials at their habitual walking speed 2‐ and 6‐months post‐ACLR. A single K‐means cluster analysis was used to identify clusters of individuals based on peak vGRF at 2‐ and 6‐months post‐ACLR. Functional waveform analyses were used to compare gait outcomes between clusters with and without controlling for gait speed and age. We identified two clusters that included a subgroup with high vGRF (n = 16) and low vGRF (n = 27). The cluster with high vGRF demonstrated greater vGRFs, knee flexion angles, and knee extension moments during early stance as compared to the low vGRF cluster 2‐ and 6‐months post‐ACLR. Individuals with peak vGRF ≥1.02 times body‐weight 2‐months post‐ACLR had 35.4 times greater odds of being assigned to the high vGRF cluster. [ABSTRACT FROM AUTHOR]

Functional chewing patterns are achieved early in life prior to other motor skills like walking. Chewing seems to improve specific aspects of attention; however, there is limited research on chewing in dual motor tasks. This study examined relationships between chewing and secondary motor tasks in children. Sixteen typically developing children (13.1 ± 2.3 years) participated in finger tapping, simple reaction time, and walking while chewing at different speeds. The chewing rates varied when produced with a secondary motor task, especially for slow chewing and preferred chewing, and the secondary motor tasks were differentially influenced by the chewing. This relationship was not as strong as what has been reported in adults. It appears the neural oscillatory mechanisms involved in chewing and the secondary motor tasks may not be fully developed in children. [ABSTRACT FROM AUTHOR]

Aging is associated with physiological changes which can manifest as age-related slowing of voluntary movements. Dual-task conditions can magnify this slowing process in older adults. The current study describes healthy adult chewing patterns and examined effects of concurrent chewing on performance of simple reaction time (RT), finger tapping, and gait. Chewing rates were measured from electromyographic (EMG) activity from the masseter muscle. Stepping rates were calculated using accelerometers mounted on the lower trunk and leg. Tapping rates were collected using accelerometers secured to a fixed surface. Simple RT was attained from a purposely designed switch. Results demonstrated that older adults walked slower, tapped slower, and had slower reaction times compared to young individuals, however chew rates were similar. This dichotomy became more pronounced when motor tasks were performed at faster speeds, with the exception being chewing. Additionally, chewing altered performance of secondary motor tasks for all individuals. Strong coupling emerged between cyclical actions (i.e., chewing-gait and chewing-tapping), reflecting entrainment between the respective neural oscillators driving the actions. In contrast, RT responses slowed appreciably when chewing was performed concurrently, indicating an interference effect. Taken together, these results illustrate the contrasting effects of chewing on a secondary motor task and highlights bidirectional effects of dual tasking on performance. [ABSTRACT FROM AUTHOR]

Highlights • The impact of chewing on walking dynamics was examined. • The walking rate of young and older adults was driven by their chewing frequency. • Older adults walked at a slower velocity compared to young adults. • No difference in chewing rates were seen between young and older adults. Abstract Chewing and walking are two oscillatory behaviors performed on an everyday basis. The current study examined the impact chewing at different speeds (i.e. fast, slow, preferred) had on walking performance for fifteen young healthy adults (23.2 + 4.2 years) and fifteen healthy older participants (66.5 + 3.2 years). Chewing rates were attained from surface EMG activity recorded from the masseter muscle. For gait, accelerometers mounted on the lower trunk and lower leg were used to determine the timing of individual steps. In addition, a pressure sensitive walkway was also used to collect gait metrics (i.e., gait velocity, step length, step time). Our results demonstrated a strong link between chewing and walking for all participants, with increases or decreases in a person's chewing rate leading to similar changes in their stepping rate (and hence walking speed). One explanation for this coupling is that the neural drive related to chewing entrains the muscles involved in the basic gait action of stepping. The coupling of stepping with chewing rates for all individuals was observed despite the older adults tending to walk slower overall. However, there were no age-related differences in chewing rates, suggesting that despite the general slowing of motor function seen with increasing age, mastication itself does not appear to be similarly affected. [ABSTRACT FROM AUTHOR]

Summary: Shewanella oneidensis is an aquatic proteobacterium with remarkable respiratory and chemotactic abilities. It is also capable of forming biofilms either associated to surfaces (SSA‐biofilm) or at the air–liquid interface (pellicle). We have previously shown that pellicle biogenesis in S. oneidensis requires the flagellum and the chemotaxis regulatory system including CheA3 kinase and CheY3 response regulator. Here we searched for additional factors involved in pellicle development. Using a multicopy library of S. oneidensis chromosomal fragments, we identified two genes encoding putative diguanylate cyclases (pdgA and pdgB) and allowing pellicle formation in the non‐pellicle‐forming cheY3‐deleted mutant. A mutant deleted of both pdgA and pdgB is affected during pellicle development. By overexpressing phosphodiesterase encoding genes, we confirmed the key role of c‐di‐GMP in pellicle biogenesis. The mxd operon, previously proposed to encode proteins involved in exopolysaccharide biosynthesis, is also essential for pellicle formation. In addition, we showed that the MxdA protein, containing a degenerate GGDEF motif, binds c‐di‐GMP and interacts with both CheY3 and PdgA. Therefore, we propose that pellicle biogenesis in S. oneidensis is controlled by a complex pathway that involves the chemotaxis response regulator CheY3, the two putative diguanylate cyclases PdgA and PdgB, and the c‐di‐GMP binding protein MxdA. [ABSTRACT FROM AUTHOR]

The WEST-project ( W -tungsten E nvironment in S teady-state T okamak) involves equipping Tore Supra with a full tungsten divertor, capable of withstanding heat load of 10 MW/m 2 in steady-state conditions, in discharges sustained by Lower Hybrid Current Drive (LHCD). The LHCD generator, recently upgraded to deliver 9.2 MW/1000 s, is equipped with sixteen TH2103C klystrons powering two launchers. The WEST transformation involves reducing the plasma volume, thus moving the launchers ∼10 cm closer to the tokamak centre. The toroidal curvature of the launchers no longer fits the plasma curvature due to the strong magnetic field ripple effect, leading to a degradation of the LH wave coupling, especially with the Full Active Multijunction Launcher (FAM). The toroidal curvature radius of the FAM launcher mouth will therefore be reshaped from 1700 mm to 2300 mm. The machining process is described in this article. In order to improve the coupling of the LH wave, the local gas injection has been modified to help to meet the requirement of 7 MW/1000 s of LH power coupled to the plasma in the WEST scenarios. Finally, the curvature radius of the waveguide septa are rounded to minimize the excitation of suprathermal electrons near the plasma edge, which can induce high power loads on the plasma facing components. [ABSTRACT FROM AUTHOR]

(1) Background: Biomechanics during landing tasks, such as the kinematics and kinetics of the knee, are altered following anterior cruciate ligament (ACL) injury and reconstruction. These variables are recommended to assess prior to clearance for return to sport, but clinicians lack access to the current gold-standard laboratory-based assessment. Inertial sensors serve as a potential solution to provide a clinically feasible means to assess biomechanics and augment the return to sport testing. The purposes of this study were to (a) develop multi-sensor machine learning algorithms for predicting biomechanics and (b) quantify the accuracy of each algorithm. (2) Methods: 26 healthy young adults completed 8 trials of a double limb jump landing task. Peak vertical ground reaction force, peak knee flexion angle, peak knee extension moment, and peak sagittal knee power absorption were assessed using 3D motion capture and force plates. Shank- and thigh- mounted inertial sensors were used to collect data concurrently. Inertial data were submitted as inputs to single- and multiple- feature linear regressions to predict biomechanical variables in each limb. (3) Results: Multiple-feature models, particularly when an accelerometer and gyroscope were used together, were valid predictors of biomechanics (R2 = 0.68–0.94, normalized root mean square error = 4.6–10.2%). Single-feature models had decreased performance (R2 = 0.16–0.60, normalized root mean square error = 10.0–16.2%). (4) Conclusions: The combination of inertial sensors and machine learning provides a valid prediction of biomechanics during a double limb landing task. This is a feasible solution to assess biomechanics for both clinical and real-world settings outside the traditional biomechanics laboratory. [ABSTRACT FROM AUTHOR]

Tuberculin skin test (TST) and IFN-γ release assays are currently used to detect Mycobacterium tuberculosis (Mtb) infection but none of them differentiate active from latent infection (LTBI). Since improved tests to diagnose Mtb infection are required, we studied the immune response to Mtb latency antigen Rv2626c in individuals exposed to the bacteria during different periods. Tuberculosis patients (TB), TB close contacts (CC: subjects exposed to Mtb for less than three months) and healthcare workers (HW: individuals exposed to Mtb at least two years) were recruited and QuantiFERON (QFT) assay, TST and IFN-γ secretion to Rv2626c were analyzed. Twenty-two percent of the individuals assessed had discordant results between QFT and TST tests. Furthermore, QFT negative and QFT positive individuals produced differential levels of IFN-γ against Rv2626c, in direct association with their exposure period to Mtb. Actually, 91% of CC QFT negative subjects secreted low levels of IFN-γ to Rv2626c, whereas 43% of HW QFT negative people produced elevated IFN-γ amounts against Rv2626c. Conversely, 69% of CC QFT positive subjects didn´t produce IFN-γ to Rv2626c. Interestingly, a similar pattern of IgG anti-Rv2626c plasma levels was observed. Therefore, determination of IFN-γ and IgG levels against the dormancy antigen Rv2626c allows to identify established LTBI. [ABSTRACT FROM AUTHOR]

Magnesium is one of the most abundant metal ions in living cells. Very specific and devoted transporters have evolved for transporting Mg2+ ions across the membrane and maintain magnesium homeostasis. Using genetic screens, we were able to identify the main players in magnesium homeostasis in the opportunistic pathogen Staphylococcus aureus. Here, we show that import of magnesium relies on the redundant activity of either CorA2 or MgtE since in absence of these two importers, bacteria require increased amounts of magnesium in the medium. A third CorA-like importer seems to play a minor role, at least under laboratory conditions. For export of magnesium, we identified two proteins, MpfA and MpfB. MpfA, is the main actor since it is essential for growth in high magnesium concentrations. We show that gain of function mutations or overexpression of the minor factor, MpfB, which is part of a sigmaB controlled stress response regulon, can compensate for the absence of MpfA. [ABSTRACT FROM AUTHOR]

Children with autism spectrum disorder (ASD) have a decreased physical fitness level when compared with their able-bodied peers. It is therefore important that new adapted exercise programs become available for children with ASD. Although adapted surfing has begun to gain popularity around the world; there is limited research on the physiological benefits for children with autism spectrum disorder. Therefore, the purpose of this study was to assess the effectiveness of an 8-week summer surf program conducted each year for six years as therapeutic recreation. We evaluated physiological and behavioral variables such as aerobic capacity, muscle strength and endurance, range of motion and personal behavior. Although there are many factors that may account for the improvements that we document in this report, this participant demonstrated improvements after each year of the surfing program. This research is the first of its kind to illustrate the effectiveness of surfing as a rehabilitative intervention in a child diagnosed with ASD. [ABSTRACT FROM AUTHOR]

It has been demonstrated that lower hybrid current drive (LHCD) systems play a crucial role for steady-state tokamak operation, owing to their high current drive (CD) efficiency and hence their capability to reduce flux consumption. This paper describes the extensive technology programmes developed for the Tore Supra (France) and the KSTAR (Korea) tokamaks in order to bring continuous wave (CW) LHCD systems into operation. The Tore Supra LHCD generator at 3.7 GHz is fully CW compatible, with RF power PRF = 9.2 MW available at the generator to feed two actively water-cooled launchers. On Tore Supra, the most recent and novel passive active multijunction (PAM) launcher has sustained 2.7 MW (corresponding to its design value of 25 MW m−2 at the launcher mouth) for a 78 s flat-top discharge, with low reflected power even at large plasma-launcher gaps. The fully active multijunction (FAM) launcher has reached 3.8 MW of coupled power (24 MW m−2 at the launcher mouth) with the new TH2103C klystrons. By combining both the PAM and FAM launchers, 950 MJ of energy, using 5.2 MW of LHCD and 1 MW of ICRH (ion cyclotron resonance heating), was injected for 160 s in 2011. The 3.7 GHz CW LHCD system will be a key element within the W (for tungsten) environment in steady-state Tokamak (WEST) project, where the aim is to test ITER technologies for high heat flux components in relevant heat flux density and particle fluence conditions. On KSTAR, a 2 MW LHCD system operating at 5 GHz is under development. Recently the 5 GHz prototype klystron has reached 500 kW/600 s on a matched load, and studies are ongoing to design a PAM launcher. In addition to the studies of technology, a combination of ray-tracing and Fokker–Planck calculations have been performed to evaluate the driven current and the power deposition due to LH waves, and to optimize the N∥ spectrum for the future launcher design. Furthermore, an LHCD system at 5 GHz is being considered for a future upgrade of the ITER Heating and Current Drive systems, with a power capability of 20 MW coupled to the plasma using a PAM launcher. An R&D programme is being conducted at CEA/IRFM to develop a BeO vacuum window which is a safety critical component of the transmission line. In addition, a mock-up of a TE10–TE30 mode converter at 5 GHz, designed for a rectangular transmission line, has been manufactured and successfully tested on Tore Supra at low RF power. [ABSTRACT FROM AUTHOR]

This year, TORE-SUPRA celebrated 25 years of operation. During this time, a number of technologies have been developed. First of all, it was mandatory to develop reliable superconducting magnets at \sim1.8~K, with superfluid helium as an efficient coolant. For the production of steady-state discharge, three types of radio-frequency (RF) additional heating systems have been developed: lower hybrid current drive, ions and electrons cyclotron resonance heating. To cope with long-lasting discharges (up to 380 s \times\,2.8 MW) and large RF additional heating power (12.3 MW \times\,3 s), actively cooled (AC) plasma facing components were deployed in TORE-SUPRA for the first time in a tokamak environment. TORE-SUPRA is now being modified into a D-shaped axisymmetric tokamak with AC main chamber walls and an AC tungsten divertor, the W—for tungsten—Environment in Steady-state tokamak (WEST). This new facility has the objective to offer ITER a test bed for validating the relevant AC metallic technologies in D-shaped H-mode plasmas. In contrast to other metallic devices such as JET and ASDEX upgrade, WEST will rely only on RF additional power systems. A set of plasma scenarios have been identified, ranging from a high total RF power scenario up to 15 MW-30 s, to a high fluence scenario of 1000 s with up to 10 MW of injected RF power. These scenarios are able to reproduce ITER-relevant conditions of steady-state heat loads of 10–20 MW/m^2, to test tungsten AC divertor technologies with relevant power heat fluxes and particle fluence. [ABSTRACT FROM AUTHOR]

This year Tore-Supra celebrated its 25 years of operation. During this long time, a number of technologies have been developed. First of all, it was mandatory to develop reliable superconducting magnets at \sim1.8~K, with superfluid helium as an efficient coolant. For the production of steady state discharge, three types of radio frequency (RF) additional heating systems have been developed: 1) lower hybrid current drive; 2) ion cyclotron resonance heating; and 3) electron cyclotron resonance heating. To cope with long lasting discharges (up to 380 s \times 2.8 MW) and large RF additional heating power (12.3 MW \times 3 s), actively cooled (AC) plasma facing components were deployed in Tore-Supra for the first time in a tokamak environment. Tore-Supra is now being modified into a D-shape axisymmetric tokamak with AC tungsten main chamber walls and a divertor, the WEST project (W-for tungsten-environment in steady-state tokamak). This new facility has the objective to offer ITER a test bed for validating the relevant AC metallic technologies in D-shape H-mode plasmas. In contrast to other metallic devices, such as JET and ASDEX Upgrade, WEST will rely only on the RF additional power systems. A set of plasma scenarios have been identified, ranging from a high total RF power scenario up to 15 MW in 30 s, to a high fluence scenario of 1000 s with up to 10 MW of injected RF power. These scenarios are able to reproduce ITER relevant conditions of steady state heat loads of 10–20 MW/m^2, to test tungsten AC divertor technologies with relevant power heat fluxes and particle fluence. [ABSTRACT FROM PUBLISHER]

In parallel to the direct contribution to the procurement phase of ITER and Broader Approach, CEA has initiated research & development programmes, accompanied by experiments together with a significant modelling effort, aimed at ensuring robust operation, plasma performance, as well as mitigating the risks of the procurement phase. This overview reports the latest progress in both fusion science and technology including many areas, namely the mitigation of superconducting magnet quenches, disruption-generated runaway electrons, edge-localized modes (ELMs), the development of imaging surveillance, and heating and current drive systems for steady-state operation. The WEST (W Environment for Steady-state Tokamaks) project, turning Tore Supra into an actively cooled W-divertor platform open to the ITER partners and industries, is presented. [ABSTRACT FROM AUTHOR]

The sustainment of steady-state plasmas in tokamaks requires efficient current drive systems. Lower hybrid current drive is currently the most efficient method to generate a continuous additional off-axis toroidal plasma current and to reduce the poloidal flux consumption during the plasma current ramp-up phase. The operation of the Tore Supra ITER-like lower hybrid (LH) launcher has demonstrated the capability to couple LH power at ITER-like power densities with very low reflected power during long pulses. In addition, the installation of eight 700 kW/CW klystrons at the LH transmitter has allowed increasing the total LH power in long-pulse scenarios. However, in order to achieve pure stationary LH-sustained plasmas, some R&D is needed to increase the reliability of all the systems and codes, from radio-frequency (RF) sources to plasma scenario prediction. The CEA/IRFM is addressing some of these issues by leading a R&D programme towards an ITER LH system and by the validation of an integrated LH modelling suite of codes. In 2011, the RF design of a mode converter was validated at a low power. A 500 kW/5 s RF window is currently under manufacture and will be tested at a high power in 2012 in collaboration with the National Fusion Research Institute. All of this work aims to reduce the operational risks associated with the ITER steady-state operations. [ABSTRACT FROM AUTHOR]