We use high‐resolution data from dayside passes of the Magnetospheric Multiscale (MMS) mission to create for the first time a comprehensive listing of encounters with the electron diffusion region ...(EDR), as evidenced by electron agyrotropy, ion jet reversals, and j • E′ > 0. We present an overview of these 32 EDR or near‐EDR events, which demonstrate a wide variety of observed plasma behavior inside and surrounding the reconnection site. We analyze in detail three of the 21 new EDR encounters, which occurred within a 1‐min‐long interval on 23 November 2016. The three events, which resulted from a relatively low and oscillating magnetopause velocity, exhibited large electric fields (up to ~100 mV/m), crescent‐shaped electron velocity phase space densities, large currents (≥2 μA/m2), and Ohmic heating of the plasma (~10 nW/m3). We include an Ohm's law analysis, in which we show that the divergence of the electron pressure term usually dominates the nonideal terms and is much more turbulent on the magnetosphere versus the magnetosheath side of the EDR.
Plain Language Summary
NASA's Magnetospheric Multiscale (MMS) mission was designed to study magnetic reconnection, a process in which oppositely directed magnetic fields embedded within two neighboring plasma populations annihilate, dumping magnetic energy into the plasmas. Previous missions studying reconnection in space were not fully equipped to analyze how the electrons in the plasma behave near the core of a reconnection site. This study provides MMS researchers with many new reconnection events to dissect, and calls special attention to three events that occurred back to back. Each event included is very unique and helps to fill in another piece of the reconnection puzzle. Perhaps the ultimate goal of these studies is to provide insight into methods of shutting down the reconnection process, which is known to impede attempts toward a stable nuclear fusion engine. A blueprint for stable nuclear fusion could solve mankind's energy needs forever.
Key Points
MMS mapped the EDR and near‐EDR several times during a sequence of new dayside encounters
Turbulence in Ohm's law terms is greatest on the magnetospheric‐side EDR, near the plane containing the X line and boundary normal vector
Thirty‐two EDR or near‐EDR encounters show crescent‐like enhancements in electron velocity space perpendicular to the local magnetic field
There is an explosive interest in 1D nanostructured materials for biological sensors. Among these nanometer‐scale materials, single‐walled carbon nanotubes (SWNTs) offer the advantages of possible ...biocompatibility, size compatibility, and sensitivity towards minute electrical perturbations. In particular, because of these inherent qualities, changes in SWNT conductivity have been explored in order to study the interaction of biomolecules with SWNTs. This Review discusses these interactions, with a focus on carbon nanotube field‐effect transistors (NTFETs). Recent examples of applications of NTFET devices for detection of proteins, antibody–antigen assays, DNA hybridization, and enzymatic reactions involving glucose are summarized. Examples of complementary techniques, such as microscopy and spectroscopy, are covered as well.
The application of carbon nanotubes in life sciences has advanced rapidly in recent years. This Review focuses on carbon‐nanotube‐based field‐effect transistors (NTFETs, see figure) as novel electrochemical transducers to give ultrasmall and highly sensitive biosensors. Recent examples of applications of NTFET devices for detection of proteins, antibody–antigen assays, DNA hybridization, and enzymatic reactions involving glucose are summarized here.
We compare case studies of Magnetospheric Multiscale (MMS)‐observed magnetopause electron diffusion regions (EDRs) to determine how the rate of work done by the electric field,
J→·(E→+v→e×B→)≡J→·E→′ ...varies with shear angle. We analyze MMS‐observed EDR event with a guide field approximately the same size as the magnetosheath reconnecting field, which occurred on 8 December 2015. We find that
J→·E→′ was largest and positive near the magnetic field reversal point, though patchy lower amplitude
J→·E→′ also occurred on the magnetosphere side EDR near the electron crescent point. The current associated with the large
J→·E→′ near the X point was carried by electrons with a velocity distribution function (VDF) resembling the magnetosheath inflow, shifted in the −v∥ direction. At the magnetosphere side EDR, the current was carried by electrons with a crescent‐like VDF. We compare this 8 December event to 10 other EDRs with different guide field strengths. The dual‐region
J→·E→′ was observed in three other moderate‐shear EDR events, whereas three high‐shear events had a strong positive
J→·E→′ near the electron crescent point and one low‐shear event had a strong positive
J→·E→′ only near the BL=0 point. The dual‐region
J→·E→′>0 was seen for one of three “intermediate”‐shear EDRs with guide fields of ∼0.2–0.3. We propose a physical relationship between the shear angle and mode of energy conversion where (a) a guide field provides an efficient mechanism for carrying a current at the field reversal point (streaming) and (b) a guide field may limit the formation of crescent electron VDFs, limiting the current carried near the stagnation point.
Plain Language Summary
At the boundary between the two, the magnetic fields of the Earth and Sun often interconnect, explosively releasing energy. This reconnection of magnetic fields takes place in a very small region of our magnetosphere's outermost boundary, but the process of reconnection effects nearly the entire magnetosphere. NASA's Magnetospheric Multiscale (MMS) mission was designed to investigate the small scale reconnection region. Within the small reconnection region, the process of exchange energy between electric fields and the surrounding plasma may depend on how the geometry of the connecting magnetic fields. Here we analyze multiple observations of the reconnection region by MMS and show that the strength of the nonreconnecting, out‐of‐the‐reconnection plane portion of the magnetic field may be a crucial factor in governing where this energy release occurs.
Key Points
We determined the location where
J→·E→′>0 for 11 asymmetric EDRs with different guide fields
Increasing the guide field strength appears to move
J→·E→′>0 from the electron crescent to the X point
Guide field allows electron streaming at X point, which takes work by the electric field
To assess the safety of the newer antiepileptic drugs (AEDs) during pregnancy.
The study population was pregnant women who enrolled in the North American AED Pregnancy Registry between 1997 and 2011. ...Data on AED use and maternal characteristics were collected through phone interviews at enrollment, at 7 months' gestation, and postpartum. Malformations were confirmed by medical records. The risk of major malformations was calculated among infants exposed to specific AEDs in monotherapy during the first trimester of pregnancy and among an unexposed group. Risk ratios (RRs) and 95% confidence intervals (CIs) were estimated with logistic regression.
The risk of major malformations was 9.3% (30 of 323) for valproate, 5.5% (11 of 199) for phenobarbital, 4.2% (15 of 359) for topiramate, 3.0% (31 of 1.033) for carbamazepine, 2.9% (12 of 416) for phenytoin, 2.4% (11 of 450) for levetiracetam, and 2.0% (31 of 1,562) for lamotrigine. Compared with lamotrigine, the RR was 5.1 (95% CI 3.0-8.5) for valproate, 2.9 (1.4-5.8) for phenobarbital, and 2.2 (1.2-4.0) for topiramate. The proportion of women with epilepsy who had seizures during pregnancy ranged from 23% for valproate to 31% for lamotrigine. Valproate was associated with a higher risk of neural tube defects, hypospadias, cardiac defects, and oral clefts and phenobarbital with a higher risk of cardiac defects and oral clefts; 5 infants exposed to topiramate (1.4%) had a cleft lip.
AEDs such as valproate and phenobarbital were associated with a higher risk of major malformations than newer AEDs such as lamotrigine and levetiracetam. Topiramate was associated with an increased risk of cleft lip compared with that of a reference population.
Electromagnetic ion cyclotron (EMIC) waves play important roles in particle loss processes in the magnetosphere. Determining the evolution of EMIC waves as they propagate and how this evolution ...affects wave‐particle interactions requires accurate knowledge of the wave vector, k. We present a technique using the curl of the wave magnetic field to determine k observationally, enabled by the unique configuration and instrumentation of the Magnetospheric MultiScale (MMS) spacecraft. The wave curl analysis is demonstrated for synthetic arbitrary electromagnetic waves with varying properties typical of observed EMIC waves. The method is also applied to an EMIC wave interval observed by MMS on October 28, 2015. The derived wave properties and k from the wave curl analysis for the observed EMIC wave are compared with the Waves in Homogenous, Anisotropic, Multi‐component Plasma (WHAMP) wave dispersion solution and with results from other single‐ and multi‐spacecraft techniques. We find good agreement between k from the wave curl analysis, k determined from other observational techniques, and k determined from WHAMP. Additionally, the variation of k due to the time and frequency intervals used in the wave curl analysis is explored. This exploration demonstrates that the method is robust when applied to a wave containing at least 3–4 wave periods and over a rather wide frequency range encompassing the peak wave emission. These results provide confidence that we are able to directly determine the wave vector properties using this multi‐spacecraft method implementation, enabling systematic studies of EMIC wave k properties with MMS.
Plain Language Summary
Waves generated within space plasmas play important roles in accelerating, heating, and depleting charged particles in Earth’s magnetosphere. The wave vector, k, mathematically relates the wavelength, direction of wave motion, and wave type to the conditions that produced it. This also tells us if a wave can interact with electrons and ions in ways that will affect the radiation belts. A key problem in understanding waves in space is that k is very difficult to determine observationally. We present a method for calculating k using Magnetospheric Multiscale (MMS) mission data. The “wave curl analysis” uses magnetic field measurements from all four MMS spacecraft to determine the electric current of the magnetic field fluctuations, which allows for direct calculation of k. We test the method on mathematically generated waveforms with properties that mimic electromagnetic ion cyclotron (EMIC) waves previously observed by MMS. We then applied this method to EMIC wave observations and compared the results to theoretical predictions and other methods for estimating k from spacecraft measurements. The wave curl analysis opens up a new way to use MMS to understand how EMIC waves are generated, how they travel and evolve, and how they affect plasma in the near‐Earth space environment.
Key Points
The wave curl analysis is a new implementation of determining k using observed wave magnetic field and associated current density
The wave curl analysis reliably determines k for both synthetic waves and Magnetospheric MultiScale observations of electromagnetic ion cyclotron waves
The calculated k is robust relative to time and frequency ranges used in the analysis, and agrees well with linear dispersion theory
The properties of acoustic speech have previously been investigated as possible cues for depression in adults. However, these studies were restricted to small populations of patients and the speech ...recordings were made during patients' clinical interviews or fixed-text reading sessions. Symptoms of depression often first appear during adolescence at a time when the voice is changing, in both males and females, suggesting that specific studies of these phenomena in adolescent populations are warranted. This study investigated acoustic correlates of depression in a large sample of 139 adolescents (68 clinically depressed and 71 controls). Speech recordings were made during naturalistic interactions between adolescents and their parents. Prosodic, cepstral, spectral, and glottal features, as well as features derived from the Teager energy operator (TEO), were tested within a binary classification framework. Strong gender differences in classification accuracy were observed. The TEO-based features clearly outperformed all other features and feature combinations, providing classification accuracy ranging between 81%-87% for males and 72%-79% for females. Close, but slightly less accurate, results were obtained by combining glottal features with prosodic and spectral features (67%-69% for males and 70%-75% for females). These findings indicate the importance of nonlinear mechanisms associated with the glottal flow formation as cues for clinical depression.
We present the result of a search of the Milagro sky map for spatial correlations with sources from a subset of the recent Fermi Bright Source List (BSL). The BSL consists of the 205 most significant ...sources detected above 100 MeV by the Fermi Large Area Telescope. We select sources based on their categorization in the BSL, taking all confirmed or possible Galactic sources in the field of view of Milagro. Of the 34 Fermi sources selected, 14 are observed by Milagro at a significance of 3 standard deviations or more. We conduct this search with a new analysis which employs newly optimized gamma-hadron separation and utilizes the full eight-year Milagro data set. Milagro is sensitive to gamma rays with energy from 1 to 100 TeV with a peak sensitivity from 10 to 50 TeV depending on the source spectrum and declination. These results extend the observation of these sources far above the Fermi energy band. With the new analysis and additional data, multi-TeV emission is definitively observed associated with the Fermi pulsar, J2229.0+6114, in the Boomerang pulsar wind nebula (PWN). Furthermore, an extended region of multi-TeV emission is associated with the Fermi pulsar, J0634.0+1745, the Geminga pulsar.
Plasma and wave measurements from the NASA Magnetospheric Multiscale mission are presented for magnetotail reconnection events on 3 July and 11 July 2017. Linear dispersion analyses were performed ...using distribution functions comprising up to six drifting bi‐Maxwellian distributions. In both events electron crescent‐shaped distributions are shown to be responsible for upper hybrid waves near the X‐line. In an adjacent location within the 3 July event a monodirectional field‐aligned electron beam drove parallel‐propagating beam‐mode waves. In the 11 July event an electron distribution consisting of a drifting core and two crescents was shown to generate upper‐hybrid and beam‐mode waves at three different frequencies, explaining the observed broadband waves. Multiple harmonics of the upper hybrid waves were observed but cannot be explained by the linear dispersion analysis since they result from nonlinear beam interactions.
Plain Language Summary
Magnetic reconnection is a process that occurs throughout the universe in ionized gases (plasmas) containing embedded magnetic fields. This process converts magnetic energy to electron and ion energy, causing phenomena such as solar flares and auroras. The NASA Magnetospheric Multiscale mission has shown that in magnetic reconnection regions there are intense electric field oscillations or waves and that electrons form crescent and beam‐like populations propagating both along and perpendicular to the magnetic field. This study shows that the observed electron populations are responsible for high‐frequency waves including their propagation directions and frequency ranges.
Key Points
Electron crescent‐shaped distributions produce upper hybrid waves in magnetotail reconnection events
Field‐aligned electron beams generate parallel electrostatic waves through the beam‐mode
Multiple crescent and convecting core distributions act together to produce broad frequency spectra as observed by MMS
This paper reports on Magnetospheric Multiscale observations of whistler mode chorus and higher‐frequency electrostatic waves near and within a reconnection diffusion region on 23 November 2016. The ...diffusion region is bounded by crescent‐shaped electron distributions and associated dissipation just upstream of the X‐line and by magnetic field‐aligned currents and electric fields leading to dissipation near the electron stagnation point. Measurements were made southward of the X‐line as determined by southward directed ion and electron jets. We show that electrostatic wave generation is due to magnetosheath electron beams formed by the electron jets as they interact with a cold background plasma and more energetic population of magnetospheric electrons. On the magnetosphere side of the X‐line the electron beams are accompanied by a strong perpendicular electron temperature anisotropy, which is shown to be the source of an observed rising‐tone whistler mode chorus event. We show that the apex of the chorus event and the onset of electrostatic waves coincide with the opening of magnetic field lines at the electron stagnation point.
Key Points
Whistler mode chorus and higher‐frequency electrostatic waves were observed in the vicinity of a reconnection diffusion region at the dayside magnetopause
The location of the Earthward boundary of chorus and electrostatic waves coincides with the opening of magnetic field lines via reconnection
The causes of whistler mode chorus and electrostatic waves are shown to be electron temperature anisotropy and beam‐plasma interactions, respectively
Chromosome 21 nondisjunction in oocytes is the most common cause of trisomy 21, the primary chromosomal abnormality responsible for Down syndrome (DS). This specific type of error is estimated to ...account for over 90 % of live births with DS, with maternal age being the best known risk factor for chromosome 21 nondisjunction. The loss of telomere length and the concomitant shortening of chromosomes are considered a biological marker for aging. Thus, we tested the hypothesis that mothers who had a maternal nondisjunction error leading to a live birth with DS (
n
= 404) have shorter telomeres than mothers with live births without DS (
n
= 42). In effect, our hypothesis suggests that mothers of children with DS will appear “biologically older” as compared to the mothers of euploid children. We applied a quantitative PCR assay to measure the genome-wide relative telomere length to test this hypothesis. The results of our study support the hypothesis that young mothers of DS babies are “biologically older” than mothers of euploid babies in the same age group and supports telomere length as a biomarker of age and hence risk for chromosome nondisjunction.
PDF
