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.

Electron magnetic reconnection without ion coupling in Earth's turbulent magnetosheath.

Magnetic reconnection in current sheets is a magnetic-to-particle energy conversion process that is fundamental to many space and laboratory plasma systems. In the standard model of reconnection, this process occurs in a minuscule electron-scale diffusion region1,2. On larger scales, ions couple to the newly reconnected magnetic-field lines and are ejected away from the diffusion region in the form of bi-directional ion jets at the ion Alfvén speed3-5. Much of the energy conversion occurs in spatially extended ion exhausts downstream of the diffusion region 6 . In turbulent plasmas, which contain a large number of small-scale current sheets, reconnection has long been suggested to have a major role in the dissipation of turbulent energy at kinetic scales7-11. However, evidence for reconnection plasma jetting in small-scale turbulent plasmas has so far been lacking. Here we report observations made in Earth's turbulent magnetosheath region (downstream of the bow shock) of an electron-scale current sheet in which diverging bi-directional super-ion-Alfvénic electron jets, parallel electric fields and enhanced magnetic-to-particle energy conversion were detected. Contrary to the standard model of reconnection, the thin reconnecting current sheet was not embedded in a wider ion-scale current layer and no ion jets were detected. Observations of this and other similar, but unidirectional, electron jet events without signatures of ion reconnection reveal a form of reconnection that can drive turbulent energy transfer and dissipation in electron-scale current sheets without ion coupling.

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.

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.

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.

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.

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.

Regional variation in life history traits and plastic responses to temperature of the major malaria vector Nyssorhynchus darlingi in Brazil.

The primary Brazilian malaria vector, Nyssorhynchus darlingi (formerly Anopheles darlingi), ranges from 0°S-23°S across three biomes (Amazonia, Cerrado, Mata Atlântica). Rising temperatures will increase mosquito developmental rates, and models predict future malaria transmission by Ny. darlingi in Brazil will shift southward. We reared F1 Ny. darlingi (progeny of field-collected females from 4 state populations across Brazil) at three temperatures (20, 24, 28 °C) and measured key life-history traits. Our results reveal geographic variation due to both genetic differences among localities and plastic responses to temperature differences. Temperature significantly altered all traits: faster larval development, shorter adult life and overall lifespan, and smaller body sizes were seen at 28 °C versus 20 °C. Low-latitude Amazonia mosquitoes had the fastest larval development at all temperatures, but at 28 °C, average development rate of high-latitude Mata Atlântica mosquitoes was accelerated and equivalent to low-latitude Amazonia. Body size of adult mosquitoes from the Mata Atlântica remained larger at all temperatures. We detected genetic variation in the plastic responses among mosquitoes from different localities, with implications for malaria transmission under climate change. Faster development combined with larger body size, without a tradeoff in adult longevity, suggests vectorial capacities of some Mata Atlântica populations may significantly increase under warming climates.

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.

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.

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.

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.

Accuracy of left ventricular end-diastolic dimension determinations obtained by radionuclide angiocardiography.

This study tested the ability of first-pass radionuclide angiocardiography to detect accurately the left ventricular endocardial surface of the intact, conscious, chronically instrumented dog. A spherical phantom was used to define the influence of collimation: with a 1.0-in. collimator, the optimal count threshold was a border at 31% of the image's maximum counts; and with a 1.5-in. collimator, the optimal count threshold was at 21%. These were used to analyze cardioscintigrams obtained in 19 studies of six dogs. The dogs were provided with pulse transit sonomicrometer dimension transducers on the endocardium, right-atrial pacing electrodes, electrocardiographic leads, and catheters in the superior vena cava and right or left atria. The minor-axis dimension of the left ventricle was measured ultrasonically while the cardioscintigram was being stored. The minor-axis dimension and end-diastolic volume obtained by the two techniques had linear correlation coefficients of 0.95 and 0.98. This correlation indicates the inherent accuracy of radionuclide techniques by defining left-ventricular endocardial edges for a large range of volumes in the dog.

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.

Curriculum for musculoskeletal radiology.

Although general suggestions have been made regarding a radiology residency curriculum, no specific list of entities has been offered. Over the past ten years, we have developed a resident-run morning conference in musculoskeletal radiology that is supervised by faculty and covers a specific curriculum. We offer our curriculum as an example that may assist other departments in developing their own curricula.

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.

Correct placement of epidural steroid injections: fluoroscopic guidance and contrast administration.

We prospectively evaluated 316 caudal-approach epidural steroid injections given by staff radiologists and residents in our department over a 1-year period. Needle placement was checked with fluoroscopy and corrected if necessary. When the needle tip was within the sacral canal, nonionic contrast material was injected. If epidural contrast was not observed, the needle tip was repositioned. Of 111 procedures performed by physicians who had given fewer than 10 epidural steroid injections, 53 (47.7%) resulted in correct nonfluoroscopically directed placement of the needle. For physicians who had performed between 10 and 50 such procedures, 62 (53.4%) of 116 had correct nonfluoroscopically directed placement. For staff physicians, 55 (61.7%) of 89 placements were correct. Even when the sacral hiatus was easily palpated and a staff physician was confident that he or she was within the epidural space, fluoroscopy revealed incorrect placement 14.2% of the time (seven of 49 procedures). In addition, when the needle was positioned within the sacral canal and no blood was evident on Valsalva maneuver or aspiration, the injection was venous in 29 of 316 procedures (9.2%). The presence of blood on the needle stylus was not a reliable indicator of venous placement of the needle. Our findings indicate that fluoroscopy is essential for correct placement of epidural steroid injection. Contrast administration is necessary to avoid venous injection of steroids.

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.

The functional significance of sacroiliitis and ankylosing spondylitis in Reiter's syndrome.

The frequent development of sacroiliitis and ankylosing spondylitis (AS) in patients suffering from Reiter's Syndrome (RS) has been stressed by a number of authors. This study was designed to ascertain the frequency of these problems in our RS patients, whether they were related to other clinical features of RS and what was the extent of the resulting disability. Fifty-five patients (50 men and 5 women) with RS with a mean duration of 9.3 years were assessed radiologically to determine the prevalence of sacroiliitis and thoracolumbar syndesmophyte formation. These radiological findings were correlated with HLA-B27, clinical features and functional status. Sacroiliitis was found in 22 patients (40%) but was mild in severity, frequently asymmetrical and very rarely associated with syndesmophyte formation. Sacroiliitis occurred significantly more commonly in patients with iritis and/or a prolonged disease duration (p less than 0.05) but although it was also found more frequently in HLA-B27 positive patients this was not significant (0.1 greater than p greater than 0.05). Some restriction in back movement was observed in 31 patients (56.3%) but only two patients satisfied New York criteria for AS and just one was functionally impaired by his back disease. Although the frequent finding of sacroiliitis in RS may provide an interesting insight into the interrelationship between RS and AS, our study shows that this sacroiliitis is commonly asymptomatic and does not provide a problem in management.