Influence of childhood maltreatment on prevalence, onset, and persistence of psychiatric comorbidities and suicide attempts in bipolar disorders.

BACKGROUND: Psychiatric comorbidities and suicide attempts are highly prevalent in Bipolar Disorders (BD). We examined the associations between childhood maltreatment, psychiatric comorbidities, and suicide attempts, in terms of lifetime prevalence, sequence of onset, and current symptoms. METHODS: We assessed 3,047 individuals with BD for suicide attempts, anxiety disorders, substance use disorders, and eating disorders. Participants completed a self-report for the assessment of childhood maltreatment. Associations between childhood maltreatment and characteristics of comorbidities (lifetime prevalence, current symptoms, and age at onset) were examined using logistic regressions and network analyses. RESULTS: Psychiatric comorbidities were frequent with a mean number per individual of 1.23 (SD = 1.4). Most comorbidities occurred prior to the onset of BD. Participants who reported higher levels of childhood maltreatment had more frequent and multiple comorbidities, which were also more currently active at inclusion. Childhood maltreatment did not decrease the age of onset of comorbidities, but was associated with a faster accumulation of comorbidities prior to the onset of BD. Logistic regression and network analyses showed that emotional abuse and sexual abuse might play a prominent role in the lifetime prevalence of psychiatric comorbidities and suicide attempts. CONCLUSIONS: Childhood maltreatment was associated with suicide attempts, and with frequent, multiple, and persistent psychiatric comorbidities that accumulated more rapidly prior to the onset of BD. Hence, childhood maltreatment should be systematically assessed in individuals with BD, in particular when the course of the disorder is characterized by a high comorbid profile or by a high suicidality.

The Frail'BESTest: an adaptation of the "balance evaluation system test" for frail older adults; Concurrent validity, responsiveness, validity for fall prediction and detection of slower walkers.

BACKGROUND: The Frail'BESTest was developed in order to include frail older adults when they are using the BESTest. Recently, psychometrics properties (internal coherence, systems usefulness, complementarity and inter-rater reliability) of the Frail'BESTest were tested. To complete these analyses, this study will aim the assessment of its concurrent validity, responsiveness, predictive validity on falls occurrence, and slower walkers detection. METHODS: The correlation between the Frail'BESTest and the Gait Speed Test permitted to assess concurrent validity. The variation between the initial test score and the score obtained after the completion of a rehabilitation program was used to evaluate responsiveness with MANOVA analysis and standard response mean (SRM) calculation. Predictive validity was assessed with receiver-operating characteristic curves and area under the curve (AUC) analysis regarding falls occurrence. Slower walkers detection thresholds were computed by receiver-operating characteristic curves for the Frail'BESTest and the Tinetti test. RESULTS: The concurrent validity of the test was good (r = 0.74; p < 0.001). The Standard Error of measurement was at 2.81 points and the Minimal Detectable Change at 7.79 points for the total score of the Frail'BESTest. The SRM was at 0.41 for the Tinetti test and 0.56 for the Frail'BESTest. The AUC, computed according to fall occurrence, was at 0.71 for the Gait Speed test, 0.673 for the Tinetti test and 0.693 for the Frail'BESTest. Both the Tinetti (AUC = 0.87) and the Frail'BESTest (AUC = 0.88) were found suitable for tracking slower walkers. CONCLUSION: Concurrent validity and responsiveness of the Frail'BESTest were good. As for the Tinetti and the Frail'BESTest, they were unable to predict efficiently falls occurrence in the tested sample. The Frail'BESTest seems enough sensitive to spot the slower walkers efficiently, using a 15/20 threshold method. The Frail'BESTest was found to be a valid and responsive clinical test, therefore it can be recommended as an outcome measure in clinical practice.

Network of co-expressed circadian genes, childhood maltreatment and sleep quality in bipolar disorders.

Bipolar disorder (BD) is a chronic and burdensome psychiatric disease, characterized by variations in mood and energy. The literature has consistently demonstrated an association between BD and childhood maltreatment (CM), and genetic variants of circadian genes have been associated with an increased vulnerability to develop BD. In this context, environmental factors such as CM may also contribute to the susceptibility to BD through alterations in the functioning of the biological clock linked to modifications of expression of circadian genes. In this study, we explored the associations between childhood maltreatment, sleep quality, and the level of expression of a comprehensive set of circadian genes in lymphoblastoid cell lines from patients with BD. The sample consisted of 52 Caucasian euthymic patients with a diagnosis of BD type 1 or type 2. The exposure to CM was assessed with the Childhood Trauma Questionnaire (CTQ), and the sleep quality was assessed using the Pittsburgh Sleep Quality Index. We measured the expression of 18 circadian genes using quantitative RT-PCR: ARNTL2, BHLHE40, BHLHE41, CLOCK, CRY1, CRY2, CSNK1D, CSNK1E, DBP, GSK3B, NPAS2, NR1D1, PER1, PER2, PER3, PPARGC1A, RORA, and RORB. Gene expression networks were analyzed with the disjoint graphs method. Compared to the other investigated transcripts, PPARGC1A was the only one whose expression level was differentially affected in patients who have experienced CM and, more specifically, physical abuse. We observed no significant effects of the other CTQ subscores (emotional and sexual abuses, physical and emotional neglects), nor of the sleep quality on the network of circadian genes expression. Although requiring replication in larger cohorts, the result obtained here is consistent with the hypothesis of an influence of CM exposure on circadian systems and highlights the importance of PPARGC1A in these processes.

The Frail'BESTest. An Adaptation of the "Balance Evaluation System Test" for Frail Older Adults. Description, Internal Consistency and Inter-Rater Reliability.

INTRODUCTION: The Balance Evaluation System Test (BESTest) and the Mini-BESTest were developed to assess the complementary systems that contribute to balance function. These tests include functional tasks involving several high-level exercises to assess the balance function, which may be even more difficult in case of frailty. The Frail'BESTest has been developed to make it possible to include frail older adults in systemic assessment. In this first paper, the objective is to present the Frail'BESTest and to describe the usefulness and complementarity of each system and to test the inter-rater reliability of the score measurements in two health centers. METHODS: In the first center, 192 frail and non-frail older patients were enrolled to test I) the contribution of each system, II) internal consistency, and III) the threshold and ceiling effects. The scores of 32 patients from center 1 and 32 patients recruited in another center (center 2) were used to measure the inter-rater reliability of the measurements by means of Kendall's tau coefficients. RESULTS: The internal consistency was moderate to good for five systems and limited for "biomechanical constraints". The distribution of the Frail'BESTest was more centered than that of the Tinetti and Mini-Motor tests. The Kendall's tau showed strong concordance in center 1 for all systems and only for 4 on 6 systems in center 2. DISCUSSION: Completing a systemic evaluation, the therapist may prioritize the patient's needs identifying the most challenging systems. This paper presents the Frail'BESTest and confirms the psychometric properties at a first step level.

Childhood maltreatment and HPA axis gene expression in bipolar disorders: A gene network analysis.

INTRODUCTION: Bipolar disorder (BD) is highly associated with childhood maltreatment (CM), the exposure to such early adversity being suggested to disrupt the expression of several biological pathways. This study aims at exploring associations between the mRNA levels of 9 HPA axis genes in lymphoblastoid cell lines from patients with BD according to their self-reported exposure to CM. METHODS: The sample consisted of 33 Caucasian patients with a diagnosis of BD type 1, assessed for the exposure to CM with the Childhood Trauma Questionnaire (CTQ). Quantitative RT-PCR was performed on 9 transcripts of the HPA axis genes: DGKH, FKBP5, NR3C1, SGK1, SGK2, SGK3, SKA2, STAT5A and UCN. RT-qPCR data were analyzed using the method of disjoint gene networks with SARP.compo package for R. RESULTS: We found no associations between CTQ total score and the amount of HPA axis transcripts neither in univariate analyses, nor with network analyses. Emotional abuse (EA) was associated with a significant decreased expression of two transcripts, DGKH (p = 0.009) and NR3C1 (p = 0.04). This was confirmed by the disjoint network analysis, which showed that NR3C1 and DGKH were expressed differently from the rest of the HPA axis network in presence of emotional abuse. DISCUSSION: This study described the expression levels of a comprehensive set of HPA axis genes according to childhood maltreatment in a sample of patients with BD type 1 and suggested that emotional abuse decreased the expression of NR3C1 and DGKH. Our results require further replication in independent larger samples.

Density-controlled quantum Hall ferromagnetic transition in a two-dimensional hole system.

Quantum Hall ferromagnetic transitions are typically achieved by increasing the Zeeman energy through in-situ sample rotation, while transitions in systems with pseudo-spin indices can be induced by gate control. We report here a gate-controlled quantum Hall ferromagnetic transition between two real spin states in a conventional two-dimensional system without any in-plane magnetic field. We show that the ratio of the Zeeman splitting to the cyclotron gap in a Ge two-dimensional hole system increases with decreasing density owing to inter-carrier interactions. Below a critical density of ~2.4 × 1010 cm-2, this ratio grows greater than 1, resulting in a ferromagnetic ground state at filling factor ν = 2. At the critical density, a resistance peak due to the formation of microscopic domains of opposite spin orientations is observed. Such gate-controlled spin-polarizations in the quantum Hall regime opens the door to realizing Majorana modes using two-dimensional systems in conventional, low-spin-orbit-coupling semiconductors.

Barriers to physical activity in coronary artery disease patients: Development and validation of a new scale.

OBJECTIVE: To develop and validate a self-report questionnaire to measure barriers to regular physical activity (PA) in patients with stable coronary artery disease (CAD). METHODS: Phase 1: 17 patients completed a semi-structured interview. After grouping and reformulating the reported barriers, their pertinence was reevaluated by the patients. Then, a decision algorithm was used to select items. A principal component analysis was performed to determine content validity. Phase 2: 49 patients completed the questionnaire resulting from phase 1 twice, 7 days apart, and questionnaires to evaluate depression, anxiety, and the level of physical activity. Construct validity was evaluated by analysis of Spearman's correlation coefficient between the total score for the questionnaire and a convergent dimension (anxiety), as well as a divergent dimension (Dijon physical activity score). Internal consistency was evaluated by Cronbach's alpha coefficient. Test-retest reliability was evaluated by the intraclass coefficient (ICC). RESULTS: Eleven items were selected after phase 1. The questionnaire presented good face validity and the content validity seemed satisfactory after analysis of the literature by the experts. Construct validity was moderate. Internal consistency was very good (Cronbach's α>0.81). Reproducibility was excellent with an ICC at 0.95. Feasibility was good with less than 3minutes to complete the questionnaire. CONCLUSION: This questionnaire presents good psychometric properties. A further prospective study should evaluate sensitivity to change and help determine a threshold value indicating the need for a specific behavioral strategy to alleviate barriers to physical activity in these patients.

High-mobility capacitively-induced two-dimensional electrons in a lateral superlattice potential.

In the presence of a lateral periodic potential modulation, two-dimensional electrons may exhibit interesting phenomena, such as a graphene-like energy-momentum dispersion, Bloch oscillations, or the Hofstadter butterfly band structure. To create a sufficiently strong potential modulation using conventional semiconductor heterostructures, aggressive device processing is often required, unfortunately resulting in strong disorder that masks the sought-after effects. Here, we report a novel fabrication process flow for imposing a strong lateral potential modulation onto a capacitively induced two-dimensional electron system, while preserving the host material quality. Using this process flow, the electron density in a patterned Si/SiGe heterostructure can be tuned over a wide range, from 4.4 × 10(10) cm(-2) to 1.8 × 10(11) cm(-2), with a peak mobility of 6.4 × 10(5) cm(2)/V·s. The wide density tunability and high electron mobility allow us to observe sequential emergence of commensurability oscillations as the density, the mobility, and in turn the mean free path, increase. Magnetic-field-periodic quantum oscillations associated with various closed orbits also emerge sequentially with increasing density. We show that, from the density dependence of the quantum oscillations, one can directly extract the steepness of the imposed superlattice potential. This result is then compared to a conventional lateral superlattice model potential.

The involvement of ankle muscles in maintaining balance in the upright posture is higher in elderly fallers.

The purpose of this study was to determine whether the mechanical contribution of ankle muscles in the upright stance differed among young adults (YA) (n=10, age: ~24.3), elderly non-fallers (ENF) (n=12, age: ~77.3) and elderly fallers (EF) (n=20, age: ~80.7). Torque and electromyographic (EMG) activity were recorded on the triceps surae and tibialis anterior during maximum and submaximum contractions in the seated position. EMG activity was also recorded in subjects standing still. Plantar flexor (PF) and dorsal flexor (DF) torques generated in the upright posture were estimated from the torque-EMG relationship obtained during submaximum contractions in the seated position. Center of pressure (CoP) displacement was measured to quantify postural stability. Results showed that, in upright standing, EF generated greater ankle muscle relative torque (i.e. PF+DF torque in the upright stance/PF+DF during maximum isometric torque) than non-fallers (i.e. ENF, YA). The greater involvement of ankle muscles in EF was associated with higher CoP displacement. PF+DF torque in the upright stance was no different among the groups, but PF+DF torque during maximum effort was impaired in older groups compared with YA and was lower in EF than ENF. These results suggest that the postural stability impairment observed with aging is highly related to ankle muscle weakness.

Clinical effectiveness and safety of a distraction-rotation knee brace for medial knee osteoarthritis.

OBJECTIVE: Evaluation of the clinical effectiveness and safety of a new custom-made valgus knee brace (OdrA) in medial knee osteoarthritis (OA) in terms of pain and secondary symptoms. METHODS: Open-label prospective study of patients with symptomatic medial knee OA with clinical evaluation at 6 and 52 weeks (W6, W52). We systematically assessed pain on a visual analog scale (VAS), Knee injury and Osteoarthritis Outcome Score (KOOS), spatio-temporal gait variables, use of nonsteroidal anti-inflammatory drugs (NSAIDs) and analgesic-sparing effects of the brace and tolerance. Mean scores were compared at baseline, W6 and W52 and the effect size (ES) and 95% confidence intervals (95% CIs) were calculated. RESULTS: We included 20 patients with knee OA (mean age 64.2±10.2 years, mean body mass index 27.2±5.4 kg/m2). VAS pain and KOOS were improved at W6 and W52: pain (ES=0.9 at 1 year), amelioration of other symptoms (ES=0.4), and function in activities of daily living (ES=1.1), sports and leisure (ES=1.5), quality of life (ES=0.9) and gait speed (ES=0.41). In total, 76% of patients showed clinical improvement at 1 year. Analgesic and NSAIDs consumption was significantly decreased at W6 and W52. One serious adverse effect noted was lower-limb varices, and observance was deemed satisfactory at 1 year. CONCLUSION: This new unloader brace appeared to have good effect on medial knee OA, with an acceptable safety profile and good patient compliance.

Test-retest reliability and responsiveness of centre of pressure measurements in patients with hip osteoarthritis.

OBJECTIVE: The aim of this study was to determine a set of measures for the evaluation of balance in patients suffering from hip osteoarthritis (OA) that were both reliable and responsive to change. DESIGN: Three groups of subjects; Healthy, hip OA patients without surgery, and hip OA with surgery (pre and post-surgery) were included in this study. Subjects had to perform balance tests in two positions: standard and narrowed stance. CoP-based measures test-retest reliability was assessed in hip OA without surgery group, responsiveness were assessed between all groups and between pre and post-surgery. RESULTS: Intraclass Correlation Coefficient (ICC) values from hip OA without surgery ranged from -0.03 to 0.9 for only five parameters (CoP path length, SD velocity, mean velocity, and antero-posterior Root Mean Square (RMS(AP)) having values over 0.7. SD velocity and RMS(AP) showed significant differences between healthy and surgery group in standard stance whereas narrowed stance revealed most differences between all groups. RMS(AP) showed the best responsiveness (Standardized Response Mean ∼0.5) between pre vs post-surgery in both conditions. RMS(AP) was also capable of discriminating between hip OA with surgery vs without surgery groups with good sensitivity and specificity. CONCLUSIONS: Our results showed there to be reliability and responsiveness of five postural parameters in hip OA patients in two conditions of standing balance. More parameters were significantly different in narrowed stance whereas sensitivity was better in standard stance. SD velocity and RMS(AP) discriminate between degrees of OA severity and highlight potential balance deficits even after arthroplasty. Selected parameters during standing balance could be assessed to complete the set of quantitative measures to quantify hip OA patient deficiencies.

Are first ventilatory threshold and 6-minute walk test heart rate interchangeable? A pilot study in healthy elderlies and cardiac patients.

BACKGROUND: Heart rate (HR) at the ventilatory threshold (VT) is often used to prescribe exercise intensity in cardiac rehabilitation. Some studies have reported no significant difference between HR at VT and HR measured at the end of a 6-min walk test (6-MWT) in cardiac patients. The aim of this work was to assess the potential equivalence between those parameters at the individual level. METHOD: Three groups of subjects performed a stress test and a 6-MWT: 22 healthy elderlies (GES, 77 ± 3.7 years), 10 stable coronary artery disease (CAD) patients (GMI, 50.9 ± 4.2 years) and 30 patients with chronic heart failure (GHF, 63.3 ± 10 years). We analyzed the correlation, mean bias, 95% confidence interval (95% CI) of the mean bias and the magnitude of the bias between 6-MWT-HR and VT-HR. RESULTS: There was a significant difference between 6-MWT and VT-HR in GHF (99.1 ± 8.8 vs 91.6 ± 18.6 bpm, P=0.016) but not in GES and GMI. The correlation between those 2 parameters was high for GMI (r=0.78, P<0.05), and moderate for GES and GHF (r=0.48 and 0.55, respectively, P<0.05). The 95% CI of bias was large (>30%) in GES and GHF and acceptable in GMI (8-12%). CONCLUSION: 6-MWT-HR and VT-HR do not appear interchangeable at the individual level in healthy elderlies and CHF patients. In CAD patients, further larger studies and/or the development of other walk tests could help in confirming the interest of a training prescription based on walking performance, after an exhaustive study of their cardiometabolic requirements.

A classification study of kinematic gait trajectories in hip osteoarthritis.

The clinical evaluation of patients in hip osteoarthritis is often done using patient questionnaires. While this provides important information it is also necessary to continue developing objective measures. In this work we further investigate the studies concerning the use of 3D gait analysis to attain this goal. The gait analysis was associated with machine learning methods in order to provide a direct measure of patient control gait discrimination. The applied machine learning method was the support vector machine (SVM). Applying the SVM on all the measured kinematic trajectories, we were able to classify individual patient and control gait cycles with a mean success rate of 88%. With the use of an ROC curve to establish the threshold number of cycles necessary for a subject to be identified as a patient, this allowed for an accuracy of higher than 90% for discriminating patient and control subjects. We then went on to determine the importance of each trajectory. By ranking the capacity of each trajectory for this discrimination, we provided a guide on their order of importance in evaluating patient severity. In order to be clinically relevant, any measure of patient deficit must be compared with clinically validated scores of functional disability. In the case of hip osteoarthritis (OA), the WOMAC scores are currently one of the most widely accepted clinical scores for quantifying OA severity. The kinematic trajectories that provided the best patient-control discrimination with the SVM were found to correlate well but imperfectly with the WOMAC scores, hence indicating the presence of complementary information in the two.

1D-1D Coulomb drag signature of a Luttinger liquid.

One-dimensional (1D) interacting electronic systems exhibit distinct properties when compared to their counterparts in higher dimensions. We report Coulomb drag measurements between vertically integrated quantum wires separated by a barrier only 15 nanometers wide. The temperature dependence of the drag resistance is measured in the true 1D regime where both wires have less than one 1D subband occupied. As a function of temperature, an upturn in the drag resistance is observed below a temperature T* ~ 1.6 kelvin. This crossover in Coulomb drag behavior is consistent with Tomonaga-Luttinger liquid models for the 1D-1D drag between quantum wires.

Sex differences in blood flow restricted isotonic knee extensions to fatigue.

AIM: It has been shown that females have greater muscular endurance than males and that this advantage is eliminated when blood flow is restricted. It is unknown if sex differences in dynamic endurance exist during low-load blood flow restricted (BFR) resistance exercise. The purpose of this study was to investigate sex differences in quadriceps femoris fatigability during isotonic knee extension exercise coupled with a blood flow restriction. METHODS: Ten males and ten females completed three sets of low-load isotonic knee extension exercises (20% of peak torque) to volitional failure under two conditions: blood flow restricted (BFR) and non-restricted free flow (FF). The number of repetitions, exercise volume, post-exercise strength loss and surface electromyography (EMG) were measured. RESULTS: Females performed more repetitions than males in the FF (252±37 vs. 112±17 repetitions; P<0.01) and BFR conditions (165±29 vs. 79±8 repetitions; P<0.01). Both sexes performed ~30% fewer repetitions during the BFR condition. MVC torque decreased approximately 37% following both conditions (P<0.01) and EMG activity increased (P<0.05) during the exercise bouts. CONCLUSION: Similar fatigue characteristics were evident in FF and BFR conditions for both sexes, and females demonstrated greater endurance, as determined by the number of repetitions completed, in both conditions. It may be beneficial to increase the relative exercise load for females in order to decrease the time under BFR.

Eccentric training in chronic heart failure: feasibility and functional effects. Results of a comparative study.

OBJECTIVES: To evaluate, in chronic heart failure (CHF) patients, feasibility, safety, compliance and functional improvements of an eccentric (ECC) cycle training protocol personalized by the rate of perceived exertion (RPE; 9-11 Borg Scale), compared to concentric (CON) training at workload corresponding to the first ventilatory threshold. METHODS: Thirty patients were randomly allocated to ECC or CON training (20 sessions). Compliance was evaluated with RPE, visual analog scale for muscle soreness and monitoring of heart rate (HR). Functional parameters were measured by the distance walked and the VO(2) uptake during the 6-minute walk test (6MWT) before and after training. RESULTS: Two patients were excluded due to adverse effects in each group. RPE was 9-11 in ECC training while it reached 12-14 in CON training. HR remained stable in ECC group during exercise whereas it increased during CON exercise. 6MWT distance improved in both group (ECC: +53 m; CON: +33 m). 6MWT VO(2) uptake remained stable in ECC group whereas it increased in CON group. CONCLUSION: ECC training tailored by RPE appears to be an efficient and safe alternative for CHF patients. Indeed, it induces functional improvement similar to conventional CON training with lower demand on the cardiovascular system during exercise.

3 Different types of strength training in older women.

The objective of the present study was to evaluate and compare the neuromuscular, morphological and functional adaptations of older women subjected to 3 different types of strength training. 58, healthy women (67 ± 5 year) were randomized to experimental (EG, n=41) and control groups (CG, n=17) during the first 6 weeks when the EG group performed traditional resistance exercise for the lower extremity. Afterwards, EG was divided into three specific strength training groups; a traditional group (TG, n=14), a power group (PG, n=13) that performed the concentric phase of contraction at high speed and a rapid strength group (RG, n=14) that performed a lateral box jump exercise emphasizing the stretch-shortening-cycle (SSC). Subjects trained 2 days per week through the entire 12 weeks. Following 6 weeks of generalized strength training, significant improvements occurred in EG for knee extension one-repetition (1RM) maximum strength (+19%), knee extensor muscle thickness (MT, +15%), maximal muscle activation (+44% average) and onset latency ( -31% average) for vastus lateralis (VL), vastus medialis (VM) and rectus femoris (RF) compared to CG (p<0.05). Following 6 more weeks of specific strength training, the 1RM increased significantly and similarly between groups (average of +21%), as did muscle thickness of the VL (+25%), and activation of VL (+44%) and VM (+26%). The onset latency of RF (TG=285 ± 109 ms, PG=252 ± 76 ms, RG=203 ± 43 ms), reaction time (TG=366 ± 99 ms, PG=274 ± 76 ms, RG=201 ± 41 ms), 30-s chair stand (TG=18 ± 3, PG=18 ± 1, RG=21 ± 2) and counter movement jump (TG=8 ± 2 cm, PG=10 ± 3 cm, RG=13 ± 2 cm) was significantly improved only in RG (p<0.05). At the end of training, the rate of force development (RFD) over 150 ms (TG=2.3 ± 9.8 N·s(-1), PG=3.3 ± 3.2 N·s(-1), RG=3.8 ± 6.8 N·s(-1), CG=2.3 ± 7.0 N·s(-1)) was significantly greater in RG and PG than in TG and CG (p<0.05). In conclusion, rapid strength training is more effective for the development of rapid force production of muscle than other specific types of strength training and by consequence, better develops the functional capabilities of older women.

Reproducibility, validity and responsiveness of the 200-metre fast walk test in patients undergoing cardiac rehabilitation.

OBJECTIVE: To investigate the reliability, validity and responsiveness of the 200-metre fast walk test in patients with coronary artery disease engaged in a cardiac rehabilitation programme. DESIGN: Descriptive study. SETTING: Tertiary care hospital. SUBJECTS: Thirty stable patients with coronary artery disease (51.9 ± 8.7 years), referred to the cardiac rehabilitation department after an acute coronary syndrome. INTERVENTION: Not applicable. MAIN MEASURES: Six-minute walk test distance, time to perform the 200-m fast walk test, peak power output of the graded maximal exercise test, before and after the programme; SF-36 quality of life questionnaire at baseline. Walk tests were performed twice at baseline to assess reliability. RESULTS: The 200-m fast walk test was highly reliable (ICC = 0.97). It was significantly correlated with the graded maximal exercise test peak power and the 6-minute walk test at baseline (r = -0.417; P < 0.05; and r = -0.566; P < 0.01, respectively) and after the training programme (r = -0.460, P < 0.05; and r = -0.926; P < 0.01, respectively). At baseline, there was a strong correlation between the 200-m fast walk test time and the physical component score of the SF-36 (r = -0.77; P < 0.01), but not between the 200-m fast walk test time and the SF-36 mental component score. Mean 200-m fast walk test time was significantly different between the patients performing ≤90 W (n = 11) or ≥100 W (n = 19) at the baseline graded maximal exercise test (121.7 ± 13.6 vs. 115.5 ± 10.1 seconds; P < 0.05). The responsiveness was strong with a standardized response mean at 1.11. CONCLUSION: The 200-m fast walk test is a reliable, valid and responsive high-intensity walk test in patients with coronary artery disease after an acute coronary syndrome. It can thus give additional information to that given by the 6-minute walk test and the graded maximal exercise test.

Positive and negative Coulomb drag in vertically integrated one-dimensional quantum wires.

Electron interactions in and between wires become increasingly complex and important as circuits are scaled to nanometre sizes, or use reduced-dimensional conductors such as carbon nanotubes, nanowires and gated high-mobility two-dimensional electron systems. This is because the screening of the long-range Coulomb potential of individual carriers is weakened in these systems, which can lead to phenomena such as Coulomb drag, where a current in one wire induces a voltage in a second wire through Coulomb interactions alone. Previous experiments have demonstrated Coulomb electron drag in wires separated by a soft electrostatic barrier of width ≳80 nm (ref. 12), which was interpreted as resulting entirely from momentum transfer. Here, we measure both positive and negative drag between adjacent vertical quantum wires that are separated by ∼15 nm and have independent contacts, which allows their electron densities to be tuned independently. We map out the drag signal versus the number of electron sub-bands occupied in each wire, and interpret the results both in terms of momentum-transfer and charge-fluctuation induced transport models. For wires of significantly different sub-band occupancies, the positive drag effect can be as large as 25%.