bluuebunny/crossref_metadata_2025_split huggingface dataset:
Study of equatorial E region irregularities using rare daytime VHF scintillation observations
Authors: Yadav V. , Kakad B. , Pant T. K. , Bhattacharyya A. , Prasad D. S. V. V. D. 
Published: September 2015

AbstractScintillations on VHF radio signal are sparsely observed during daytime due to unavailability of strong electron density irregularities in equatorial E or F region. Type I/II irregularities observed at E region altitudes during the daytime are linked with either two‐stream or gradient drift instability. The occurrence of these irregularities in presence of strong blanketing Es (Esb) can produce weak‐moderate scintillations on VHF signal during daytime. Such sparse daytime VHF scintillations are used in the present study to retrieve information about E region irregularities, which are generally examined with radar observations. We use spaced receiver scintillation observations on 251 MHz signal transmitted from geostationary satellite UFO2 (71.2°E) and recorded at Tirunelveli (8.5°N, 77.8°E, dip latitude 0.6°N). Ionosonde data from Trivandrum (8.5°N, 76.6°E, dip latitude 0.5°N) during 2003–2005 is used to confirm the association of daytime scintillations with Esb. The daytime scintillations last for 15–45 min during postnoon hours. Their occurrence closely matches the peak occurrence time of Esb. For the first time, spatial scale lengths of E region irregularities are obtained using the technique introduced by Bhattacharyya et al. (2003). The observed spatial scales are validated using theoretical model. The theoretical model manifests 6–19% density fluctuations in the E region to produce weak scintillations (0.15 ≤S4≤ 0.4) on 251 MHz. The study reveals that scale lengths of E region irregularities are smaller on counter equatorial electrojet (CEEJ) days than non‐CEEJ days, which could be resulting from lower electron temperatures in E region on CEEJ days.
Auroral spirals at Saturn
Authors: Radioti A. , Grodent D. , Gérard J.‐C. , Roussos E. , Mitchell D. , Bonfond B. , Pryor W. 
Published: September 2015

AbstractWe report observations of auroral spirals at Saturn propagating from midnight to noon via dawn, based on Cassini/UVIS measurements. The aurora during that sequence is observed for the first time to consist of detached features swirling as they propagate from dawn to early afternoon. The features have a diameter of ∼6000 km in the ionosphere, which would correspond to 12 to 15 RS wide plasma regions in the magnetosphere. Simultaneous ENA enhancements are observed; however, they do not show a clear spiral form. We estimate the velocity of the UV auroral features to decrease from 85% of rigid corotation (28°/h) near the equatorward edge to 68% of rigid corotation (22°/h) in the poleward edge. We discuss two possible scenarios which could explain the generation of the auroral spirals. First, we suggest that the auroral spirals could be related to large dynamic hot populations which create regions with strong velocity gradients. Alternatively, a less possible theory could be that the auroral spirals are related to field line deformation from the magnetosphere to the ionosphere, similar to the scenario proposed to explain auroral spirals at Earth. Such field line twist can happen for a configuration where the magnetospheric source region is located between a pair of plasma flow vortices.
Statistical characterization of the growth and spatial scales of the substorm onset arc
Authors: Kalmoni N. M. E. , Rae I. J. , Watt C. E. J. , Murphy K. R. , Forsyth C. , Owen C. J. 
Published: September 2015

AbstractWe present the first multievent study of the spatial and temporal structuring of the aurora to provide statistical evidence of the near‐Earth plasma instability which causes the substorm onset arc. Using data from ground‐based auroral imagers, we study repeatable signatures of along‐arc auroral beads, which are thought to represent the ionospheric projection of magnetospheric instability in the near‐Earth plasma sheet. We show that the growth and spatial scales of these wave‐like fluctuations are similar across multiple events, indicating that each sudden auroral brightening has a common explanation. We find statistically that growth rates for auroral beads peak at low wave number with the most unstable spatial scales mapping to an azimuthal wavelength λ≈ 1700–2500 km in the equatorial magnetosphere at around 9–12 RE. We compare growth rates and spatial scales with a range of theoretical predictions of magnetotail instabilities, including the Cross‐Field Current Instability and the Shear Flow Ballooning Instability. We conclude that, although the Cross‐Field Current instability can generate similar magnitude of growth rates, the range of unstable wave numbers indicates that the Shear Flow Ballooning Instability is the most likely explanation for our observations.
Dust storm and electron density in the equatorial D region ionosphere of Mars: Comparison with Earth's ionosphere from rocket measurements in Brazil
Authors: Haider S. A. , Batista I. S. , Abdu M. A. , Muralikrishna P. , Shah Siddhi Y. , Kuroda T. 
Published: September 2015

AbstractWe report the first model result for the dust densities and electron densities in the D region ionosphere of Mars for aerosol particles of different sizes during a major dust storm that occurred in Martian Year (MY) 25 at low latitude. These calculations are made at latitude 10°S and solar longitudes (Ls) = 200°, 220°, 250°, and 280° for high, medium, low, and absence of dust storms, respectively. Four corresponding dust layers were found at 50 km, 50 km, 38 km, and 25 km during these events. During high dust storm period, the optical depth and dust density increased by a factor of ~20 from its normal condition. The electron densities estimated for the D region ionosphere of Mars for submicron sized dust particles are largest as compared to that estimated for larger particles. The electron density reduced by ~2 orders of magnitude during high dust storm. The estimated electron density in the clear atmosphere of Mars is compared with measurements of Earth's ionosphere at nearly the same geophysical condition.
Thermal electron acceleration by electric field spikes in the outer radiation belt: Generation of field‐aligned pitch angle distributions
Authors: Vasko I. Y. , Agapitov O. V. , Mozer F. S. , Artemyev A. V. 
Published: September 2015

AbstractVan Allen Probes observations in the outer radiation belt have demonstrated an abundance of electrostatic electron‐acoustic double layers (DL). DLs are frequently accompanied by field‐aligned (bidirectional) pitch angle distributions (PAD) of electrons with energies from hundred eVs up to several keV. We perform numerical simulations of the DL interaction with thermal electrons making use of the test particle approach. DL parameters assumed in the simulations are adopted from observations. We show that DLs accelerate thermal electrons parallel to the magnetic field via the electrostatic Fermi mechanism, i.e., due to reflections from DL potential humps. The electron energy gain is larger for larger DL scalar potential amplitudes and higher propagation velocities. In addition to the Fermi mechanism, electrons can be trapped by DLs in their generation region and accelerated due to transport to higher latitudes. Both mechanisms result in formation of field‐aligned PADs for electrons with energies comparable to those found in observations. The Fermi mechanism provides field‐aligned PADs for <1 keV electrons, while the trapping mechanism extends field‐aligned PADs to higher‐energy electrons. It is shown that the Fermi mechanism can result in scattering into the loss cone of up to several tenths of percent of electrons with flux peaking at energies up to several hundred eVs.
Plasma sheet Pi2 pulsations associated with bursty bulk flows
Authors: Xing Xiaoyan , Wang Chih‐Ping , Liang Jun , Lyons Larry R. 
Published: September 2015

AbstractThere is a debate as to whether magnetic Pi2 pulsations (0.006–0.025 Hz) observed in the plasma sheet and on the ground are triggered by the earthward moving bursty bulk flows (BBFs) from midtail or distant tail or are caused by the substorm plasma instabilities initiated in the near‐Earth plasma sheet. To resolve this debate, we conducted case and statistical studies of enhanced plasma sheet Pi2 pulsations using Time History of Events and Macroscale Interactions during Substorms (THEMIS) observations from X~−30 RE to X~−8 RE. The case studies show that for both substorm‐related and quiet time BBFs, enhanced Pi2 oscillations are observed in front of BBFs from midtail to the near‐Earth plasma sheet. The oscillations intensify 1–4 min prior to the substantial flow enhancement, and usually initiate within several narrow discrete frequency bands, with lower frequencies intensifying earlier. We further examined the wave properties using low‐frequency MHD fitting method and found that one or more discrete waves for each event are magnetosonic waves. Our statistical study of 364 BBFs shows that Pi2 pulsations are commonly associated with BBFs throughout the plasma sheet. The lowest‐frequency oscillations usually appear below 0.01 Hz, and the strongest power oscillations appear at ~0.01 Hz or higher frequencies. We found that over 75% of the discrete oscillations are magnetosonic waves, and that 70%–75% of them are slow mode. These suggest that plasma sheet Pi2 pulsations are likely triggered by BBFs in the entire plasma sheet regardless of substorm onsets.
Power line harmonic radiation observed by the DEMETER spacecraft at 50/60 Hz and low harmonics
Authors: Němec F. , Parrot M. , Santolík O. 
Published: September 2015

AbstractWe present a low‐altitude satellite survey of Power Line Harmonic Radiation (PLHR), i.e., electromagnetic waves radiated by electric power systems on the ground. We focus on frequencies corresponding to the first few harmonics of the base power system frequencies (50 Hz or 60 Hz, depending on the region). It is shown that the intensities of electromagnetic waves detected at these frequencies at an altitude of about 700 km are significantly enhanced above industrialized areas. The frequencies at which the wave intensities are increased are in excellent agreement with base power system frequencies just below the satellite location. We also investigate a possible presence of the weekend effect, i.e., if the situation is different during the weekends when the power consumption is lower than during the weekdays. Such an effect might be possibly present in the European region, but it is very weak. PLHR effects are less often detected in the summer, as the ionospheric absorption increases, and also, the radiation is obscured by lightning generated emissions. This difference is smaller in the U.S. region, in agreement with the monthly variations of the power consumption. The analysis of the measured frequency spectra reveals that although intensity increases at low odd harmonics of base power system frequencies are routinely detected, low even harmonics are generally absent. Finally, we verify the relation of PLHR intensities to the geomagnetically induced currents (GICs) proxy. It is shown that the PLHR intensity is increased at the times of higher GIC proxy values during the night.
Association of Lupus Anticoagulant With Long‐Term Damage Accrual in Antineutrophil Cytoplasmic Antibody–Associated Vasculitis
Authors: Jordan Natasha , D'cruz David P. 
Published: September 2015

ObjectiveAntiphospholipid antibodies (aPL) are frequently present in antineutrophil cytoplasmic antibody–associated vasculitis (AAV) patients; however, the prognostic impact of aPL in such patients has not been elucidated. The objective of this study was to determine whether persistent aPL positivity in AAV patients was associated with increased long‐term damage accrual.MethodsClinical data were retrospectively collected on all AAV patients who attended the vasculitis clinic at our center over a 4‐year period. Data collection included presence of lupus anticoagulant (LAC) and IgG and IgM anticardiolipin (aCL) antibody titers, along with concurrent diagnosis of antiphospholipid syndrome (APS). Accumulation of long‐term damage was quantified using the Vasculitis Damage Index (VDI).ResultsData from 116 AAV patients were analyzed. A total of 34% (n = 40) had persistently positive aCL or LAC or a concurrent diagnosis of APS and were classified as AAV/aPL. A total of 76 patients (66%) were classified as AAV alone. LAC was present in a statistically higher proportion of AAV/aPL patients than those in the AAV‐alone group (P < 0.0001). Mean VDI score was significantly higher in the AAV/aPL group at mean ± SD 3.54 ± 1.36 as compared to 1.96 ± 1.42 in the AAV‐alone group (P < 0.0001). Major vascular damage scores were significantly higher in the AAV/aPL group, with mean ± SD 0.32 ± 0.59 as compared to 0.07 ± 0.26 in the AAV‐alone group (P < 0.007).ConclusionPersistently positive occurrence of aPL, in particular LAC, is present in a significant proportion of AAV patients and is associated with a higher VDI score. Clinicians should consider screening AAV patients for aPL.
Choosing Wisely in Daily Practice: An Intervention Study on Antinuclear Antibody Testing by Rheumatologists
Authors: Lesuis Nienke , Hulscher Marlies E. J. L. , Piek Ester , Demirel Hatice , van der Laan‐Baalbergen Nicole , Meek Inger , van Vollenhoven Ronald F. , den Broeder Alfons A. 
Published: September 2015

ObjectiveTo assess the effect of a simple intervention on antinuclear antibody (ANA) test overuse by rheumatologists.MethodsThis was an explorative, pragmatic, before‐and‐after, controlled implementation study among rheumatologists working at 3 rheumatology departments in secondary and tertiary care centers in The Netherlands. The intervention was given in all study centers separately and combined education with feedback. Six outcome measures describe the intervention effects: the ANA/new patient ratio (APR), difference with the target APR, percentage of positive ANA tests, percentage of repeated ANA testing, percentage of ANA‐associated diseases, and APR variation between rheumatologists. Outcomes were compared between the pre‐ and postintervention period (both 12 months) using (multilevel) logistic regression or F testing. Results are reported together for centers 1 and 2, and separately for center 3, because ANA tests could not be linked to an individual rheumatologist in center 3.ResultsThe APR decreased from 0.37 to 0.11 after the intervention in centers 1 and 2 (odds ratio [OR] 0.19, 95% confidence interval [95% CI] 0.17–0.22, P < 0.001) and from 0.45 to 0.30 in center 3 (OR 0.53, 95% CI 0.45–0.62, P < 0.001). The percentage of repeated ANA requests in all centers and the APR variation for centers 1 and 2 decreased significantly. Only in center 3 did the percentage of ANA‐associated diseases increase significantly.ConclusionA simple intervention resulted in a relevant and significant decrease in the numbers of ANA tests requested by rheumatologists, together with an improvement on 3 other outcome measures.
Asymptomatic Versus Symptomatic Ankle Joints in Rheumatoid Arthritis: A High‐Resolution B‐Mode and Power Doppler Ultrasound Study
Authors: Alsuwaidi Mohammed , Ehrenstein Boris , Fleck Martin , Hartung Wolfgang 
Published: September 2015

ObjectiveAnkle joints are frequently neglected in activity scoring systems, including the Disease Activity Score in 28 joints (DAS28). Only a few studies have assessed pathologies detected by ultrasonography of the ankles in symptomatic rheumatoid arthritis (RA) patients. We evaluated ankle joints in RA patients regardless of symptomatology, using musculoskeletal ultrasound (MSUS) as well as power Doppler ultrasound (PDUS).MethodsA total of 160 ankle joints of 80 RA patients were examined using MSUS and PDUS, according to the European League Against Rheumatism MSUS guidelines. Additionally, the talonavicular joints (TNJs) and the medial and the lateral tendon compartments were examined. The visual analog scale (VAS) score was recorded for each patient.ResultsA total of 80 RA patients with a median age of 60 years and disease duration of 5 years were enrolled in our study. The median DAS28 score was 5. A total of 97 ankles were painful (VAS 1–10), whereas 63 ankles were asymptomatic (VAS 0). Overall, the predominant pathology was arthritis of the tibiotalar joint (TTJ) and/or TNJ in 124 ankles (77%), followed by tenosynovitis of the medial compartment tendons in 44 ankles (28%). Arthritis of the TTJ was present in 59% and synovitis of the TNJ in 35% of the symptomatic ankles. In asymptomatic ankles, TTJ synovitis was detected in 35%, whereas TNJ arthritis was observed in 18%. PDUS activity was higher in the subgroup of symptomatic ankles.ConclusionThe most frequent pathologies detected by MSUS were arthritis of the TTJ and TNJ, followed by tenosynovitis of the medial compartment tendons. Pathologic findings were more frequent in symptomatic but also common in asymptomatic patients, whereas PDUS activity was generally low and mainly observed in symptomatic patients.
Work Outcome in Patients With Ankylosing Spondylitis: Results From a 12‐Year Followup of an International Study
Authors: Castillo‐Ortiz J. D. , Ramiro S. , Landewé R. , van der Heijde D. , Dougados M. , van den Bosch F. , Boonen A. 
Published: September 2015

ObjectiveTo understand the impact of ankylosing spondylitis (AS) on work disability (WD) over 12 years compared with the general population, and explore factors predicting adverse work outcome, defined as new partial WD or reduction in working hours.MethodsSource of data was the Outcome Assessments in Ankylosing Spondylitis International Study, which includes patients from The Netherlands, France, and Belgium. Standardized WD rates over time compared to the general population were calculated using indirect standardization (Dutch patients only). Cox survival analyses identified baseline predictors as well as time‐varying factors influencing adverse work outcome over 12 years.ResultsOf 215 patients, 55 (26%) were full WD at baseline and 139 (65%) were at risk for adverse work outcome during followup. When compared to the general population, WD over 12 years continued to be increased in Dutch men (incidence rate [IR] 2.9 [95% confidence interval (95% CI) 1.2, 4.6]), but less clearly for women (IR 1.2 [95% CI −0.4, 2.9]). Within the entire sample, baseline predictors of adverse work outcome over 12 years were residence in The Netherlands (versus France or Belgium) (hazard ratio [HR] 3.4 [95% CI 1.4, 8.4]) and worse Bath Ankylosing Spondylitis Functional Index (BASFI) (HR 1.2 [95% CI 1.0, 1.4]). Time‐varying predictors over 12 years were residence in The Netherlands, uveitis, and either BASFI or Bath Ankylosing Spondylitis Disease Activity Index with age and inflammatory bowel disease.ConclusionAlthough WD was already prevalent at inclusion in the cohort, a substantial proportion of patients incurred further adverse work outcome over 12 years. In addition to country of residence, uveitis, age, and self‐reported physical function or disease activity predicted long‐term adverse work outcome.
Clinical Characteristics of Sarcoid Arthropathy: A Population‐Based Study
Authors: Ungprasert Patompong , Crowson Cynthia S. , Matteson Eric L. 
Published: September 2015

ObjectiveThe epidemiology and clinical characteristics of sarcoid arthropathy are not well described, as only referral‐based studies have been reported. This study aimed to use the data from a geographically well‐defined population to characterize the clinical characteristics of sarcoid arthropathy.MethodsAn inception cohort of patients with incident sarcoidosis in the years 1976–2013 in a geographically well‐defined population was identified based on comprehensive individual medical records review. Inclusion required physician diagnosis supported by histopathology and radiologic features of intrathoracic sarcoidosis, compatible clinical presentation, and exclusion of other granulomatous diseases. Patients with joint pain were then identified from this cohort.ResultsIn 1976–2013, all 345 incident cases of sarcoidosis were identified. Symptoms of joint pain occurred in 42 patients (mean age 41.2 years, 57.1% female, and 95% white), and 35 patients had swollen joint(s) on physical examination. Most patients had arthralgia prior to the diagnosis of sarcoidosis, with an average time to diagnosis of 21 days. Of the 35 cases, oligoarthritis (2 to 4 joints) was the most common pattern (88% of cases), followed by monoarthritis (6%) and polyarthritis (6%). Ankles were involved in 91% of cases. In the majority of patients (88%), the arthritis resolved within 6 weeks. Classic Lofgren's syndrome was observed in 11 patients (26%).ConclusionInflammatory arthritis occurs in a minority of patients with sarcoidosis. Acute oligoarthritis with bilateral ankle involvement was the most common pattern of sarcoid arthropathy. It should be noted that the generalizability of the results may be limited, as the cohort was predominantly white.
Relation of Step Length to Magnetic Resonance Imaging–Detected Structural Damage in the Patellofemoral Joint: The Multicenter Osteoarthritis Study
Authors: Stefanik Joshua J. , Gross K. Douglas , Guermazi Ali , Felson David T. , Roemer Frank W. , Niu Jingbo , Lynch John A. , Segal Neil A. , Lewis Cora E. , Lewis Cara L. 
Published: September 2015

ObjectiveTo investigate the relationship of step length to the sex‐specific prevalence and worsening of magnetic resonance imaging (MRI)–detected structural damage in the patellofemoral (PF) joint among a cohort of older women and men with or at risk of knee osteoarthritis (OA).MethodsThe Multicenter Osteoarthritis Study is a cohort study of persons ages 50–79 years with or at risk of knee OA. Step length was assessed using the GAITRite walkway (CIR Systems) at the 60‐month visit, and cartilage damage and bone marrow lesions (BMLs) were graded on MRI at the 60‐ and 84‐month visits. Step length was divided into sex‐specific quintiles, and the relationship of step length to the prevalence and worsening of cartilage damage and BMLs in the PF joint was examined using logistic regression, adjusting for age, body mass index (BMI), leg length, and tibiofemoral joint structural damage.ResultsIn 1,053 knees, 4,094 and 4,083 PF joint subregions were studied for the cartilage and BML analyses, respectively. Mean ± SD age was 65.6 ± 8.1 years and mean ± SD BMI was 29.1 ± 4.7 kg/m2; 62% of participants were female. In women, compared to those with the shortest step length, those with the longest step length had 0.62 (95% confidence interval [95% CI] 0.43–0.88) and 0.59 (95% CI 0.40–0.87) times the odds of cartilage damage and BMLs, respectively. There was no cross‐sectional association in men, and no longitudinal association in either sex.ConclusionWomen with PF joint structural damage may adapt their gait by shortening their step length, but this may not be sufficient to reduce the risk of worsening damage over time.