Fine-time energetic electron behavior observed by Cluster/RAPID in the magnetotail associated with X-line formation and subsequent current disruption

Energetic electrons with 90deg pitch angle have been observed in the magnetotail at ~19 <i>R<sub>E</sub></i> near local midnight during the recovery phase of a substorm event on 27 August 2001 (Baker et al., 2002). Based on auroral images Baker et al. (2002) placed the substorm expansion phase between ~04:06:16 and ~04:08:19 UT. The electron enhancements perpendicular to the ambient magnetic field occurred while the Cluster spacecraft were on closed field lines in the central plasma sheet approaching the neutral sheet. Magnetic field and energetic particle measurements have been employed from a number of satellites, in order to determine the source and the subsequent appearance of these electrons at the Cluster location. It is found that ~7.5 min after an X-line formation observed by Cluster (Baker et al., 2002) a current disruption event took place inside geosynchronous orbit and subsequently expanded both in local time and tailward, giving rise to field-aligned currents and the formation of a current wedge. A synthesis of tail reconnection and the cross-tail current disruption scenario is proposed for the substorm global initiation process: When a fast flow with northward magnetic field, produced by magnetic reconnection in the midtail, abruptly decelerates at the inner edge of the plasma sheet, it compresses the plasma populations earthward of the front, altering dynamically the B<sub>z</sub> magnetic component in the current sheet. This provides the necessary and sufficient conditions for the kinetic cross-field streaming/current (KCSI/CFCI) instability (Lui et al., 1990, 1991) to initiate. As soon as the ionospheric conductance increases over a threshold level, the auroral electrojet is greatly intensified (see Fig. 2 in Baker et al., 2002), which leads to the formation of the substorm current wedge and dipolarization of the magnetic field. This substorm scenario combines the near-Earth neutral line and the current disruption for the initiation of substorms, at least during steady southward IMF. One can conclude the following: The observations suggest that the anisotropic electron increases observed by Cluster are not related to an acceleration mechanism associated with the X-line formation in the midtail, but rather these particles are generated in the dusk magnetospheric sector due to the longitudinal and tailward expansion of a current disruption region and subsequently observed at the Cluster location with no apparent energy dispersion.<br><br> <b>Keywords.</b> Magnetospheric physics (Magnetotail; Plasma convection; Storms and substorms

Dipolarization fronts in the near-Earth space and substorm dynamics

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Simulation Analysis of Air Flow and Turbulence Statistics in a Rib Grit Roughened Duct

The implementation of variable artificial roughness patterns on a surface is an effective technique to enhance the rate of heat transfer to fluid flow in the ducts of solar air heaters. Different geometries of roughness elements investigated have demonstrated the pivotal role that vortices and associated turbulence have on the heat transfer characteristics of solar air heater ducts by increasing the convective heat transfer coefficient. In this paper we investigate the two-dimensional, turbulent, unsteady flow around rectangular ribs of variable aspect ratios by directly solving the transient Navier-Stokes and continuity equations using the finite elements method. Flow characteristics and several aspects of turbulent flow are presented and discussed including velocity components and statistics of turbulence. The results reveal the impact that different rib lengths have on the computed mean quantities and turbulence statistics of the flow. The computed turbulence parameters show a clear tendency to diminish downstream with increasing rib length. Furthermore, the applied numerical method is capable of capturing small-scale flow structures resulting from the direct solution of Navier-Stokes and continuity equations

Characteristics and determinants of endurance cycle ergometry and six-minute walk distance in patients with COPD

BACKGROUND: Exercise tolerance can be assessed by the cycle endurance test (CET) and six-minute walk test (6MWT) in patients with Chronic Obstructive Pulmonary Disease (COPD). We sought to investigate the characteristics of functional exercise performance and determinants of the CET and 6MWT in a large clinical cohort of COPD patients. METHODS: A dataset of 2053 COPD patients (43% female, age: 66.9 ± 9.5 years, FEV(1)% predicted: 48.2 ± 23.2) was analyzed retrospectively. Patients underwent, amongst others, respiratory function evaluation; medical tests and questionnaires, one maximal incremental cycle test where peak work rate was determined and two functional exercise tests: a CET at 75% of peak work rate and 6MWT. A stepwise multiple linear regression was used to assess determinants. RESULTS: On average, patients had impaired exercise tolerance (peak work rate: 56 ± 27% predicted, 6MWT: 69 ± 17% predicted). A total of 2002 patients had CET time of duration (CET-T(end)) less than 20 min while only 51 (2.5%) of the patients achieved 20 min of CET-T(end) . In former patients, the percent of predicted peak work rate achieved differed significantly between men (48 ± 21% predicted) and women (67 ± 31% predicted). In contrast, CET-T(end) was longer in men (286 ± 174 s vs 250 ± 153 s, p < 0.001). Also, six minute walking distance (6MWD) was higher in men compared to women, both in absolute terms as in percent of predicted (443 m, 67%predicted vs 431 m, 72%predicted, p < 0.05). Gender was associated with the CET-T(end) but BMI, FEV(1) and FRC were related to the 6MWD highlighting the different determinants of exercise performance between CET and 6MWT. CONCLUSIONS: CET-T(end) is a valuable outcome of CET as it is related to multiple clinical aspects of disease severity in COPD. Gender difference should temper the interpretation of CET

Effect of interval compared to continuous exercise training on physiological responses in patients with Chronic Respiratory Diseases: a systematic review and meta-analysis

Background: Current evidence suggests that interval (IET) and continuous exercise training (CET) produce comparable benefits in exercise capacity, cardiorespiratory fitness and symptoms in patients with chronic obstructive pulmonary disease (COPD). However, the effects of these modalities have only been reviewed in patients with COPD. . This meta-analysis compares the effectiveness of IET versus CET on exercise capacity, cardiorespiratory fitness and exertional symptoms in patients with chronic respiratory diseases (CRDs). Methods: PubMed, CINHAL, Scopus, Cochrane Central Register of Controlled Trials (CENTRAL) and Nursing and Allied health were searched for randomised controlled trials from inception to September 2020. Eligible studies included the comparison between IET and CET, reporting measures of exercise capacity, cardiorespiratory fitness and symptoms in individuals with CRDs. Results: Thirteen randomised control trials (530 patients with CRDs) with fair to good quality on the PEDro scale were included. Eleven studies involved n=446 patients with COPD, one involved n=24 patients with cystic fibrosis (CF) and one n=60 lung transplantation candidates (LT). IET resulted in greater improvements in peak work rate (2.40 W, 95% CI: 0.83 to 3.97 W; p=0.003) and lower exercise-induced dyspnoea (–0.47, 95% CI: -0.86 to 0.09; p=0.02) compared to CET, however these improvements did not exceed the minimal importance difference for these outcomes. No significant differencesin peak oxygen uptake, heart rate, minute ventilation, lactate threshold and leg discomfort were found between the interventions. Conclusions: IET is superior to CET in improving exercise capacity and exercise-induced dyspnoea sensations in patients with CRDs, however the extent of the clinical benefit is not considered clinically meaningful

Home-based maintenance tele-rehabilitation reduces the risk for acute exacerbations of COPD, hospitalisations and emergency department visits

Pulmonary rehabilitation (PR) remains grossly underutilised by suitable patients worldwide. We investigated whether home-based maintenance tele-rehabilitation will be as effective as hospital-based maintenance rehabilitation and superior to usual care in reducing the risk for acute chronic obstructive pulmonary disease (COPD) exacerbations, hospitalisations and emergency department (ED) visits. Following completion of an initial 2-month PR programme this prospective, randomised controlled trial (between December 2013 and July 2015) compared 12 months of home-based maintenance tele-rehabilitation (n=47) with 12 months of hospital-based, outpatient, maintenance rehabilitation (n=50) and also to 12 months of usual care treatment (n=50) without initial PR. In a multivariate analysis during the 12-month follow-up, both home-based tele-rehabilitation and hospital-based PR remained independent predictors of a lower risk for 1) acute COPD exacerbation (incidence rate ratio (IRR) 0.517, 95% CI 0.389–0.687, and IRR 0.635, 95% CI 0.473–0.853), respectively, and 2) hospitalisations for acute COPD exacerbation (IRR 0.189, 95% CI 0.100–0.358, and IRR 0.375, 95% CI 0.207–0.681), respectively. However, only home-based maintenance tele-rehabilitation and not hospital-based, outpatient, maintenance PR was an independent predictor of ED visits (IRR 0.116, 95% CI 0.072–0.185). Home-based maintenance tele-rehabilitation is equally effective as hospital-based, outpatient, maintenance PR in reducing the risk for acute COPD exacerbation and hospitalisations. In addition, it encounters a lower risk for ED visits, thereby constituting a potentially effective alternative strategy to hospital-based, outpatient, maintenance PR

Energetic Particle Observations and Propagation in the Three-Dimensional Heliosphere During the 2006 December Events

We report observations of solar energetic particles obtained by the HI-SCALE and COSPIN/LET instruments onboard Ulysses during the period of isolated but intense solar activity in 2006 December, in the declining phase of the solar activity cycle. We present measurements of particle intensities and also discuss observations of particle anisotropies and composition in selected energy ranges. Active Region 10930 produced a series of major solar flares with the strongest one (X9.0) recorded on December 5 after it rotated into view on the solar east limb. Located over the South Pole of the Sun, at >72°S heliographic latitude and 2.8 AU radial distance, Ulysses provided unique measurements for assessing the nature of particle propagation to high latitudes under near-minimum solar activity conditions, in a relatively undisturbed heliosphere. The observations seem to exclude the possibility that magnetic field lines originating at low latitudes reached Ulysses, suggesting either that the energetic particles observed as large solar energetic particle (SEP) events over the South Pole of the Sun in 2006 December were released when propagating coronal waves reached high-latitude field lines connected to Ulysses, or underwent perpendicular diffusion. We also discuss comparisons with energetic particle data acquired by the STEREO and Advanced Composition Explorer in the ecliptic plane near 1 AU during this period