Publisher Correction: Electron magnetic reconnection without ion coupling in Earth's turbulent magnetosheath

Change history: In this Letter, the y-axis values in Fig. 3f should go from 4 to -8 (rather than from 4 to -4), the y-axis values in Fig. 3h should appear next to the major tick marks (rather than the minor ticks), and in Fig. 1b, the arrows at the top and bottom of the electron-scale current sheet were going in the wrong direction; these errors have been corrected online.

Kinetic Range Spectral Features of Cross Helicity Using the Magnetospheric Multiscale Spacecraft

We study spectral features of ion velocity and magnetic field correlations in the magnetosheath and in the solar wind using data from the Magnetospheric Multiscale (MMS) spacecraft. High-resolution MMS observations enable the study of the transition of these correlations between their magnetofluid character at larger scales into the subproton kinetic range, previously unstudied in spacecraft data. Cross-helicity, angular alignment, and energy partitioning is examined over a suitable range of scales, employing measurements based on the Taylor frozen-in approximation as well as direct two-spacecraft correlation measurements. The results demonstrate signatures of alignment at large scales. As kinetic scales are approached, the alignment between v and b is destroyed by demagnetization of protons.

Electron-scale dynamics of the diffusion region during symmetric magnetic reconnection in space

Magnetic reconnection is an energy conversion process that occurs in many astrophysical contexts including Earth's magnetosphere, where the process can be investigated in situ by spacecraft. On 11 July 2017, the four Magnetospheric Multiscale spacecraft encountered a reconnection site in Earth's magnetotail, where reconnection involves symmetric inflow conditions. The electron-scale plasma measurements revealed (i) super-Alfvénic electron jets reaching 15,000 kilometers per second; (ii) electron meandering motion and acceleration by the electric field, producing multiple crescent-shaped structures in the velocity distributions; and (iii) the spatial dimensions of the electron diffusion region with an aspect ratio of 0.1 to 0.2, consistent with fast reconnection. The well-structured multiple layers of electron populations indicate that the dominant electron dynamics are mostly laminar, despite the presence of turbulence near the reconnection site.

Direct measurements of two-way wave-particle energy transfer in a collisionless space plasma

Particle acceleration by plasma waves and spontaneous wave generation are fundamental energy and momentum exchange processes in collisionless plasmas. Such wave-particle interactions occur ubiquitously in space. We present ultrafast measurements in Earth's magnetosphere by the Magnetospheric Multiscale spacecraft that enabled quantitative evaluation of energy transfer in interactions associated with electromagnetic ion cyclotron waves. The observed ion distributions are not symmetric around the magnetic field direction but are in phase with the plasma wave fields. The wave-ion phase relations demonstrate that a cyclotron resonance transferred energy from hot protons to waves, which in turn nonresonantly accelerated cold He⁺ to energies up to ~2 kilo-electron volts. These observations provide direct quantitative evidence for collisionless energy transfer in plasmas between distinct particle populations via wave-particle interactions.

Structure, force balance, and topology of Earth's magnetopause

The magnetopause deflects the solar wind plasma and confines Earth's magnetic field. We combine measurements made by the four spacecraft of the Magnetospheric Multiscale mission to demonstrate how the plasma and magnetic forces at the boundary affect the interaction between the shocked solar wind and Earth's magnetosphere. We compare these forces with the plasma pressure and examine the electron distribution function. We find that the magnetopause has sublayers with thickness comparable to the ion scale. Small pockets of low magnetic field strength, small radius of curvature, and high electric current mark the electron diffusion region. The flow of electrons, parallel and antiparallel to the magnetic field, reveals a complex topology with the creation of magnetic ropes at the boundary.

Transient, small-scale field-aligned currents in the plasma sheet boundary layer during storm time substorms

We report on field-aligned current observations by the four Magnetospheric Multiscale (MMS) spacecraft near the plasma sheet boundary layer (PSBL) during two major substorms on 23 June 2015. Small-scale field-aligned currents were found embedded in fluctuating PSBL flux tubes near the separatrix region. We resolve, for the first time, short-lived earthward (downward) intense field-aligned current sheets with thicknesses of a few tens of kilometers, which are well below the ion scale, on flux tubes moving equatorward/earthward during outward plasma sheet expansion. They coincide with upward field-aligned electron beams with energies of a few hundred eV. These electrons are most likely due to acceleration associated with a reconnection jet or high-energy ion beam-produced disturbances. The observations highlight coupling of multiscale processes in PSBL as a consequence of magnetotail reconnection.

Ion-scale secondary flux ropes generated by magnetopause reconnection as resolved by MMS

New Magnetospheric Multiscale (MMS) observations of small-scale (~7 ion inertial length radius) flux transfer events (FTEs) at the dayside magnetopause are reported. The 10 km MMS tetrahedron size enables their structure and properties to be calculated using a variety of multispacecraft techniques, allowing them to be identified as flux ropes, whose flux content is small (~22 kWb). The current density, calculated using plasma and magnetic field measurements independently, is found to be filamentary. Intercomparison of the plasma moments with electric and magnetic field measurements reveals structured non-frozen-in ion behavior. The data are further compared with a particle-in-cell simulation. It is concluded that these small-scale flux ropes, which are not seen to be growing, represent a distinct class of FTE which is generated on the magnetopause by secondary reconnection.

Electron-scale measurements of magnetic reconnection in space

Magnetic reconnection is a fundamental physical process in plasmas whereby stored magnetic energy is converted into heat and kinetic energy of charged particles. Reconnection occurs in many astrophysical plasma environments and in laboratory plasmas. Using measurements with very high time resolution, NASA's Magnetospheric Multiscale (MMS) mission has found direct evidence for electron demagnetization and acceleration at sites along the sunward boundary of Earth's magnetosphere where the interplanetary magnetic field reconnects with the terrestrial magnetic field. We have (i) observed the conversion of magnetic energy to particle energy; (ii) measured the electric field and current, which together cause the dissipation of magnetic energy; and (iii) identified the electron population that carries the current as a result of demagnetization and acceleration within the reconnection diffusion/dissipation region.

The effect of weight training on bone mineral density and bone turnover in postmenopausal breast cancer survivors with bone loss: a 24-month randomized controlled trial

SUMMARY

This study examined whether 24 months of weight training exercises enhanced the effectiveness of risedronate, calcium, and vitamin D in maintaining or improving bone mineral density (BMD) in 223 postmenopausal breast cancer survivors. Subjects who were > or =50% adherent to exercise had no improvement in BMD but were less likely to lose BMD.

INTRODUCTION

This study examined whether (1) postmenopausal breast cancer survivors (BCS) with bone loss taking 24 months of risedronate, calcium, and vitamin D had increased bone mineral density (BMD) at the total hip, femoral neck, L1-L4 spine, total radius and 33% radius, and decreased bone turnover; (2) subjects who also participated in strength/weight training (ST) exercises had greater increases in BMD and greater decreases in bone turnover; and (3) subjects who also exercised were more likely to preserve (at least maintain) BMD.

METHODS

Postmenopausal BCS (223) were randomly assigned to exercise plus medication or medication only groups. Both groups received 24 months of 1,200 mg of calcium and 400 IU of vitamin D daily and 35 mg of risedronate weekly, and the exercise group additionally had ST exercises twice weekly.

RESULTS

After 24 months, women who took medications without exercising had significant improvements in BMD at the total hip (+1.81%) and spine (+2.85%) and significant decreases in Alkphase B (-8.7%) and serum NTx (-16.7%). Women who also exercised had additional increases in BMD at the femoral neck (+0.29%), total hip (+0.34%), spine (+0.23%), total radius (+0.30%), and additional decreases in Alkphase B (-2.4%) and Serum NTx (-6.5%). Additional changes in BMD and bone turnover with exercise were not significant. Subjects who were > or =50% adherent to exercise were less likely to lose BMD at the total hip (chi-square [1] = 4.66, p = 0.03) and femoral neck (chi-square [1] = 4.63, p = 0.03).

CONCLUSION

Strength/weight training exercises may prevent loss of BMD in postmenopausal BCS at risk for bone loss.

Width and variation of the ENA flux ribbon observed by the Interstellar Boundary Explorer

The dominant feature in Interstellar Boundary Explorer (IBEX) sky maps of heliospheric energetic neutral atom (ENA) flux is a ribbon of enhanced flux that extends over a broad range of ecliptic latitudes and longitudes. It is narrow (approximately 20 degrees average width) but long (extending over 300 degrees in the sky) and is observed at energies from 0.2 to 6 kilo-electron volts. We demonstrate that the flux in the ribbon is a factor of 2 to 3 times higher than that of the more diffuse, globally distributed heliospheric ENA flux. The ribbon is most pronounced at approximately 1 kilo-electron volt. The average width of the ribbon is nearly constant, independent of energy. The ribbon is likely the result of an enhancement in the combined solar wind and pickup ion populations in the heliosheath.

Multifocal, metachronous, giant cell tumor of the lower limb

A case of multifocal giant cell tumor in a skeletally immature male with documented metachronous disease of the lower limb is described followed by a review of the literature including treatment options and their outcomes.

Bone mineral density in postmenopausal breast cancer survivors

PURPOSE

The overall purpose of this longitudinal 18-month study was to test the feasibility and effectiveness of a multicomponent intervention for prevention and treatment of osteoporosis. The purpose of this article is to describe the baseline bone mineral density (BMD) findings for 30 postmenopausal women and to compare these BMD findings to time since menopause, body mass index, and tamoxifen use.

DATA SOURCES

Baseline data of BMD findings for 30 postmenopausal women, who have had a variety of treatments including surgery, adjuvant chemotherapy and or tamoxifen, and are enrolled in the 18-month longitudinal study. A demographic questionnaire and a three day dietary record were used to collect baseline data.

CONCLUSIONS

Eighty percent of the women with breast cancer history had abnormal BMDs at baseline (t-scores below -1.00 SD). Thinner women showed a greater risk for accelerated trabecular bone loss at the spine and hip.

IMPLICATIONS FOR PRACTICE

These findings suggest the need for early BMD assessments and for aggressive health promotion intervention strategies that include a multifaceted protocol of drug therapy for bone remodeling, 1500 mg of daily calcium, 400 IU vitamin D and a strength weight training program that is implemented immediately following chemotherapy treatment and menopause in this high risk population of women.

Views of Earth's magnetosphere with the image satellite

The IMAGE spacecraft uses photon and neutral atom imaging and radio sounding techniques to provide global images of Earth's inner magnetosphere and upper atmosphere. Auroral imaging at ultraviolet wavelengths shows that the proton aurora is displaced equatorward with respect to the electron aurora and that discrete auroral forms at higher latitudes are caused almost completely by electrons. Energetic neutral atom imaging of ions injected into the inner magnetosphere during magnetospheric disturbances shows a strong energy-dependent drift that leads to the formation of the ring current by ions in the several tens of kiloelectron volts energy range. Ultraviolet imaging of the plasmasphere has revealed two unexpected features-a premidnight trough region and a dayside shoulder region-and has confirmed the 30-year-old theory of the formation of a plasma tail extending from the duskside plasmasphere toward the magnetopause.

The superolateral approach for aspiration of total hip arthroplasties

Hip aspiration for exclusion of infection is a common procedure prior to revision arthroplasty. Some patients with total hip arthroplasties develop superomedial migration of the prosthesis, while others can have extensive heterotopic bone formation. The traditional approaches may be contraindicated due to overlying bowel or bone anterior/lateral to the prosthesis. These patients are candidates for the superolateral approach. With the patient supine marks are made on the skin at (i) the greater trochanter and (ii) a superior site that aligns with the neck of the prosthesis and soft-tissue window. The needle enters the lateral skin parallel to the table top. Usually only one pass is necessary.

Imaging of skeletal and soft tissue injuries in and around the knee

This article addresses the place of MR imaging in the diagnosis of knee injuries. MR imaging of subtle fractures and bone contusions is described with emphasis placed on those types of fractures frequently associated with specific patterns of soft tissue injury. Soft tissue injuries are divided into ligamentous, meniscal, and muscular; each is discussed separately. The MR imaging appearance of these lesions is explained.

Risk factors for progression to new sites of radiographically defined osteoarthritis in women

OBJECTIVE

To describe the association between hormonally related risk factors and the progression to new sites of radiographically defined full body (generalized) osteoarthritis (OA) in a cohort of older women.

METHODS

A retrospective cohort design was used to study former radium dial painters over the age of 40 years who had minimal radium exposure. At study entry and at varying followup times, clinical examinations were conducted and full body radiographs were taken. Two followup groups were defined: women with a followup radiograph 1-9 years after baseline (n = 75) and 10-19 years after baseline (n = 53). Fifty-five joints (10 joint groups) were independently graded at baseline and followup for OA by the method of Kellgren and Lawrence, and provided the basis for summary full body OA progression scores. Progression was defined as an increase in the number of sites with OA and in separate analyses as an increase in the number of joint groups with OA.

RESULTS

Increasing length of followup and lower baseline OA score were associated with greater OA progression, while age at baseline examination showed no clear relation to progression. Beyond these variables, increasing height and having ever smoked were inversely associated with OA progression, while body mass index (BMI) showed a weak positive association. In multivariable modeling for followup 1-9 years, only lower baseline OA score predicted greater OA progression to new sites (partial r2 = 0.13, p = 0.0009). In followup 10-19 years, baseline OA score (partial r2 = 0.12, p = 0.0011), height (partial r2 = 0.057, p = 0.033), and smoking status (partial r2 = 0.09, p = 0.035) were independent predictors of OA progression to new sites, while greater BMI was a positive, weak, and nonsignificant predictor (partial r2 = 0.031, p = 0.29). History of prior cholecystectomy, hysterectomy, dilation and curetage, number of pregnancies, and change in BMI were not significantly related to progression of OA to new sites. Similar results were found for predictors of OA progression to new joint groups.

CONCLUSION

Lower baseline level of OA is associated with greater OA progression to new sites or joint groups independent of age, suggesting a "burnout" phenomenon. In addition, shorter height and having never smoked appear to be independent risk factors that predict the progression of radiographic OA to new sites or joint groups.

Patellar fatigue fractures

Three cases of patellar fatigue fracture are reviewed. Two fractures presented with acute displacement and were initially thought to represent pathological fractures. Histological appearances in one case, and the clinical course in another, subsequently indicated that these were fatigue fractures. A third patient developed a chronic undisplaced fracture and followed the typical clinical course of fatigue fractures at other sites. The importance of recognizing patellar fatigue fractures and of differentiating spontaneously displaced fatigue fractures from pathological fractures is emphasized.

Decreased survival with increasing prevalence of full-body, radiographically defined osteoarthritis in women

The relation between full-body, radiographically defined osteoarthritis and survival was examined in a cohort of 296 women aged 42-76 years (mean age, 57.1 years). These women were a random sample of women with very low body burdens of radium who were part of a larger cohort of women first employed in the US radium dial-painting industry between 1915 and 1945. At entry into the study between 1957 and 1982, these women had a clinical examination, and full-body radiographs were taken. Fifty-five joints (18 joint groups) of the hands, feet, cervical spine, lumbar spine, pelvis, and knees in each woman were graded for osteoarthritis by the method of J. H. Kellgren and J. S. Lawrence (Ann Rheum Dis 1957; 16:494-502). Through 1985, 18.6% (n = 55) of the women died. Cox regression showed a decreased survival for women with an increasing number of joint groups affected with osteoarthritis after adjusting for age at examination (hazard ratio = 1.45 for each increase in 3.1 joint groups (1 standard deviation) affected with osteoarthritis, 95% confidence interval 1.12-1.87). Further adjustment for a history of diabetes, smoking, alcohol use, and body mass index only slightly altered the risk. Similar results were obtained for the number of joints with osteoarthritis and the number of structures (e.g., left hand and right hand) with osteoarthritis. These results suggest that an increasing prevalence of full-body radiographic osteoarthritis is associated with decreased survival independent of age and several comorbid conditions related to osteoarthritis.

Detection of herpes simplex viral DNA in the iridocorneal endothelial syndrome

OBJECTIVE

To test the hypothesis that the iridocorneal endothelial (ICE) syndrome has a viral origin by comparing the incidence of viral DNA in corneal specimens from patients with the ICE syndrome and from controls.

DESIGN

Thirty-one corneas obtained from 25 patients with the ICE syndrome and six with chronic herpetic keratitis (n = 31) were compared with 30 control specimens obtained from 15 healthy donors and from 15 patients with other, nonviral chronic corneal diseases.

METHODS

Primer pairs and polymerase chain reaction methods were used to identify and amplify either a segment of the DNA polymerase gene in the case of the herpes simplex and zoster viruses or a region of the nuclear antigen gene for the Epstein-Barr virus. The oligonucleotide amplified by polymerase chain reaction was fully characterized with the use of restriction enzyme, hybridization, and sequence analyses to determine that it contained the expected base pair sequence.

RESULTS

Sixteen of 25 ICE syndrome specimens and four of six herpetic keratitis specimens were positive for herpes simplex virus (HSV) DNA. All nine ICE syndrome specimens tested were negative for the presence of DNA from the herpes zoster or the Epstein-Barr viruses. Controls were uniformly negative for HSV DNA whether they were obtained from ostensibly normal corneas (n = 15) or from corneas with intestinal keratitis, aphakic bullous keratopathy, or keratoconus (n = 15). Tissue samples cut from positive ICE syndrome specimens yielded negative results when retested after the endothelial layer was removed. These findings indicate that localization of HSV DNA is within the endothelium, the tissue primarily involved in the pathogenesis of the ICE syndrome.

CONCLUSIONS

Polymerase chain reaction evidence shows that HSV DNA is present in a substantial percentage of ICE syndrome corneal specimens and that HSV-DNA is absent in normal corneas and in corneas from patients with three other chronic corneal diseases. These results provide direct evidence to support our hypothesis that the ICE syndrome has a viral origin. We discussed clinical implications, including possible therapeutic interventions.

Unusual radiological features in Paget's disease of bone

The radiological diagnosis of Paget's disease of bone is usually straightforward because most cases conform to well-established classic descriptions. Diagnosis becomes more difficult, however, when radiological appearances are not typical or other disease processes mask or alter the behavior of Paget's disease. Examples are presented to illustrate four categories of unusual radiological presentation of Paget's disease: (1) unusual disease progression, (2) massive post-immobilization lysis, (3) metastatic spread to pagetic bone, and (4) vertebral end-plate destruction that mimics infection.

Comparison of a videodisc system with a conventional film file for medical student teaching

PURPOSE

The authors assessed the effectiveness of a videodisc film file compared with a conventional film file for teaching radiology to medical students.

METHODS

Fourth-year medical students (N = 134) studied 116 cases selected from the American College of Radiology Learning File. Half the students studied 58 skeletal cases using conventional films and half studied the same cases on a videodisc system. Student groups were then switched and those who studied skeletal cases on films studied 58 chest cases on videodisc and vice versa. Students received the same skeletal and chest tests and completed a questionnaire.

RESULTS

For both skeletal and chest radiology, students studying films scored minimally higher than students using the videodisc. Students rated films superior to the videodisc for amount learned, convenience of use, and ability to detect lesions.

CONCLUSIONS

Conventional film and videodisc methods resulted in similar levels of learning; however, students perceived conventional films to be a superior learning experience.

Gadolinium-enhanced MRI of soft tissue masses

The efficacy of gadopentetate dimeglumine (Gd-DTPA) enhanced magnetic resonance (MR) imaging in the diagnosis and differentiation of soft-tissue, neoplastic and non-neoplastic lesion has not been well established. Thirty patients with soft tissue masses (18 neoplastic and 12 non-neoplastic) were studied, using MR imaging with and without administration of Gd-DTPA. Gd-DTPA proved helpful in characterisation of several entities, including differentiation of solid mass from proteinaceous cyst, demonstration of tumour nodules within haemorrhagic or necrotic masses, and delineation of tumour adjacent to oedema. The use of Gd-DTPA may provide additional information for tissue specificity and, in complicated cases, Gd-DTPA may also provide essential information that cannot be obtained using other methods. We recommend the use of contrast enhanced MR as an adjunct to conventional MR imaging in the initial assessment of musculoskeletal soft tissue masses. However, T2-weighted images show better tissue contrast of the lesions, and are equal to contrast enhanced images in delineation of tumour margins. Non-contrast enhanced images are, therefore, probably adequate for the delineation of lesions for surgical planning when a diagnosis has already been made.

The use of intravenous gadopentetate dimeglumine in magnetic resonance imaging of synovial lesions

Spin echo T1- and T2-weighted images and intravenously administered gadopentetate dimeglumine-enhanced T1-weighted images were obtained in 4 normal volunteers and 11 patients (11 joints) with painful, intermittent, or persistent joint swelling of unknown etiology. These studies were retrospectively reviewed to assess the benefits of contrast-enhanced magnetic resonance imaging (MRI) in evaluating the synovium. Normal synovium and joint fluid showed no visually apparent enhancement on images obtained immediately after intravenous injection of gadopentetate dimeglumine. Abnormal synovium enhanced significantly, allowing the precise identification of equivocal or unsuspected synovial disease processes. These results suggest that, in selected cases, enhanced MRI can be a useful adjunct in the evaluation of suspected synovial disease processes.