Comparison of formulas for resonant interactions between energetic electrons and oblique whistler-mode waves

Test particle simulation is a useful method for studying both linear and nonlinear wave-particle interactions in the magnetosphere. The gyro-averaged equations of particle motion for first-order and other cyclotron harmonic resonances with oblique whistler-mode waves were first derived by Bell [J. Geophys. Res. 89, 905 (1984)] and the most recent relativistic form was given by Ginet and Albert [Phys. Fluids B 3, 2994 (1991)], and Bortnik [Ph.D. thesis (Stanford University, 2004), p. 40]. However, recently we found there was a (- 1) l - 1 term difference between their formulas of perpendicular motion for the lth-order resonance. This article presents the detailed derivation process of the generalized resonance formulas, and suggests a check of the signs for self-consistency, which is independent of the choice of conventions, that is, the energy variation equation resulting from the momentum equations should not contain any wave magnetic components, simply because the magnetic field does not contribute to changes of particle energy. In addition, we show that the wave centripetal force, which was considered small and was neglect in previous studies of nonlinear interactions, has a profound time derivative and can significantly enhance electron phase trapping especially in high frequency waves. This force can also bounce the low pitch angle particles out of the loss cone. We justify both the sign problem and the missing wave centripetal force by demonstrating wave-particle interaction examples, and comparing the gyro-averaged particle motion to the full particle motion under the Lorentz force. ? 2015 AIP Publishing LLC.SCI(E)[email protected]; [email protected]

MESSENGER observations of Alfvénic and compressional waves during Mercury's substorms

MErcury Surface, Space ENviroment, GEochemistry, and Ranging (MESSENGER) magnetic field measurements during the substorm expansion phase in Mercury's magnetotail have been examined for evidence of low‐frequency plasma waves, e.g., Pi2‐like pulsations. It has been revealed that the By fluctuations accompanying substorm dipolarizations are consistent with pulses of field‐aligned currents near the high‐latitude edge of the plasma sheet. Detailed analysis of the By fluctuations reveals that they are near circularly polarized electromagnetic waves, most likely Alfvén waves. Soon afterward the plasma sheet thickened and MESSENGER detected a series of compressional waves. These Alfvénic and compressional waves have similar durations (10–20 s), suggesting that they may arise from the same source. Drawing on Pi2 pulsation models developed for Earth, we suggest that the Alfvénic and compressional waves reported here at Mercury may be generated by the quasi‐periodic sunward flow bursts in Mercury's plasma sheet. But because they are observed during the period with rapid magnetic field reconfiguration, we cannot fully exclude the possibility of standing Alfvén wave.Key PointsThe first observation of Pi2‐like pulsations during Mercury's substormAlfvénic and compressional waves were observed in the different regions of the plasma sheetWe proposed the sources for the plasma wavesPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/113132/1/grl53278.pd

Clinical and Survival Impact of Sex-Determining Region Y-Box 2 in Colorectal Cancer: An Integrated Analysis of the Immunohistochemical Study and Bioinformatics Analysis

Transcription factor sex-determining region Y-box 2 (SOX2) involves in the maintenance of cancer stem cells. However, the role of SOX2 in colorectal cancer (CRC) remains unclear. This study was conducted to investigate the effect of SOX2 on CRC. Studies were searched using electronic databases. The combined odds ratios (ORs) or hazard ratios (HRs: multivariate Cox survival analysis) with their 95% confidence intervals (CIs) were calculated. The Cancer Genome Atlas (TCGA) and GEO datasets were further applied to validate the survival effect. The functional analysis of SOX2 was investigated. In this work, 13 studies including 2337 patients were identified, and validation data were enrolled from TCGA and GEO datasets. SOX2 expression was not significantly related to age, gender, microsatellite instability (MSI) status, clinical stage, histological grade, tumor size, pT-stage, lymph node metastasis, distal metastasis, and cancer-specific survival (CSS) but was correlated with worse overall survival (OS: n = 536 patients) (P<0.05). Furthermore, TCGA data demonstrated similar results, with no significant correlation between SOX2 and pathological characteristics. Further validation data (OS: n = 1408 and disease-free survival (DFS): n = 1367) showed that SOX2 expression was correlated with worse OS (HR = 1.35, 95% CI: 1.11–1.65, P=0.004) and DFS (HR = 1.30, 95% CI: 1.04–1.62, P=0.02). The functional analyses showed that SOX2 involved in cell-cell junction, focal adhesion, extracellular matrix- (ECM-) receptor interaction, and MAP kinase activity. Our findings suggest that SOX2 expression may be correlated with the worse prognosis of CRC

Large-scale inverted-V channels of upflowing oxygen ions pumped by Alfvén waves

Large-scale inverted-V channels of upflowing oxygen ions are frequently identified in data collected by Cluster, at all local times, near the open-closed field line boundary over Earth’s high-latitude ionosphere-occur with downward propagating MHD Alfvén waves which have cascaded into kinetic regimes of plasma. The transverse acceleration of the oxygen ions in the center of these structures is interpreted as the integrated energization by these waves along the channels. Also observed within the channels are upward parallel electric fields, a key characteristic of kinetic Alfvén waves, which may contribute not only to lifting the ions but also to precipitating aurora electrons that might initiate ion upflow in the ionosphere below. Statistics on five-year observations of Cluster show that the channels typically form during geomagnetic perturbations, particularly when solar-wind dynamic pressure is high or highly fluctuated. Near the open-closed field line boundary, the stronger the wave power, the higher the upward oxygen flux and the higher the beam energy, indicating that these waves provide a simple but efficient way to drive oxygen upflows

In Silico Prediction of the Dissociation Rate Constants of Small Chemical Ligands by 3D-Grid-Based VolSurf Method

Accumulated evidence suggests that binding kinetic properties&mdash;especially dissociation rate constant or drug-target residence time&mdash;are crucial factors affecting drug potency. However, quantitative prediction of kinetic properties has always been a challenging task in drug discovery. In this study, the VolSurf method was successfully applied to quantitatively predict the koff values of the small ligands of heat shock protein 90&alpha; (HSP90&alpha;), adenosine receptor (AR) and p38 mitogen-activated protein kinase (p38 MAPK). The results showed that few VolSurf descriptors can efficiently capture the key ligand surface properties related to dissociation rate; the resulting models demonstrated to be extremely simple, robust and predictive in comparison with available prediction methods. Therefore, it can be concluded that the VolSurf-based prediction method can be widely applied in the ligand-receptor binding kinetics and de novo drug design researches

Comparison of formulas for resonant interactions between energetic electrons and oblique whistler-mode waves

Test particle simulation is a useful method for studying both linear and nonlinear wave-particle interactions in the magnetosphere. The gyro-averaged equations of particle motion for first-order and other cyclotron harmonic resonances with oblique whistler-mode waves were first derived by Bell [J. Geophys. Res. 89, 905 (1984)] and the most recent relativistic form was given by Ginet and Albert [Phys. Fluids B 3, 2994 (1991)], and Bortnik [Ph.D. thesis (Stanford University, 2004), p. 40]. However, recently we found there was a (- 1) l - 1 term difference between their formulas of perpendicular motion for the lth-order resonance. This article presents the detailed derivation process of the generalized resonance formulas, and suggests a check of the signs for self-consistency, which is independent of the choice of conventions, that is, the energy variation equation resulting from the momentum equations should not contain any wave magnetic components, simply because the magnetic field does not contribute to changes of particle energy. In addition, we show that the wave centripetal force, which was considered small and was neglect in previous studies of nonlinear interactions, has a profound time derivative and can significantly enhance electron phase trapping especially in high frequency waves. This force can also bounce the low pitch angle particles out of the loss cone. We justify both the sign problem and the missing wave centripetal force by demonstrating wave-particle interaction examples, and comparing the gyro-averaged particle motion to the full particle motion under the Lorentz force. ? 2015 AIP Publishing LLC.SCI(E)[email protected]; [email protected]

Modulation of Whistler Mode Waves by Ion‐Scale Waves Observed in the Distant Magnetotail

Wave activities in tailward flows have been explored in the distant magnetotail at ~54 RE, where the coupling between whistler mode waves and ion‐scale waves was observed. The whistler mode waves periodically appeared at each cycle of the ion‐scale waves, and the electron distribution functions associated with the whistler mode waves showed enhancement in the direction parallel to background magnetic field. Wave analyses show that the field‐aligned electron components act as the energy source of the whistler mode waves. The ion‐scale waves are generated by the interaction of the hot ion beam with background ions. A likely candidate of the ion‐scale wave is the kinetic Alfven wave, which can generate the enhanced field‐aligned electron populations by the parallel electric field.Plain Language SummaryThe ionized particles constrained by the Earth’s magnetic field involve dynamics of different spatial and temporal scales. Because of large mass difference, the scales characterizing the ion and electron dynamics are very different, and the related processes are often considered separately. In this study, we have found that the electron scale waves can be modulated by ion‐scale waves, indicating that the dynamics of electrons and ions are coupled. The ion‐scale waves are induced by the streaming ion beams superposed on the background ions. In the process, electrons are accelerated parallel to the magnetic field direction by the ion‐scale wave, resulting in the deviation of electron populations from the equilibrium state. The unstable electrons then release the excess energy by generating electron scale waves, called whistler mode waves.Key PointsModulation of whistler mode waves by ion‐scale waves are observed in the distant magnetotailThe whistler mode waves are excited by field‐aligned electron populations generated by the ion‐scale wavesThe ion‐scale waves, possibly kinetic Alfven waves, are driven by tailward streaming ion beamsPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154258/1/jgra55507.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154258/2/jgra55507_am.pd