Tracking the Corticospinal Tract in Patients With High-Grade Glioma: Clinical Evaluation of Multi-Level Fiber Tracking and Comparison to Conventional Deterministic Approaches

While the diagnosis of high-grade glioma (HGG) is still associated with a considerably poor prognosis, neurosurgical tumor resection provides an opportunity for prolonged survival and improved quality of life for affected patients. However, successful tumor resection is dependent on a proper surgical planning to avoid surgery-induced functional deficits whilst achieving a maximum extent of resection (EOR). With diffusion magnetic resonance imaging (MRI) providing insight into individual white matter neuroanatomy, the challenge remains to disentangle that information as correctly and as completely as possible. In particular, due to the lack of sensitivity and accuracy, the clinical value of widely used diffusion tensor imaging (DTI)-based tractography is increasingly questioned. We evaluated whether the recently developed multi-level fiber tracking (MLFT) technique can improve tractography of the corticospinal tract (CST) in patients with motor-eloquent HGGs. Forty patients with therapy-naïve HGGs (mean age: 62.6 ± 13.4 years, 57.5% males) and preoperative diffusion MRI [repetition time (TR)/echo time (TE): 5000/78 ms, voxel size: 2x2x2 mm3, one volume at b=0 s/mm2, 32 volumes at b=1000 s/mm2] underwent reconstruction of the CST of the tumor-affected and unaffected hemispheres using MLFT in addition to deterministic DTI-based and deterministic constrained spherical deconvolution (CSD)-based fiber tractography. The brain stem was used as a seeding region, with a motor cortex mask serving as a target region for MLFT and a region of interest (ROI) for the other two algorithms. Application of the MLFT method substantially improved bundle reconstruction, leading to CST bundles with higher radial extent compared to the two other algorithms (delineation of CST fanning with a wider range; median radial extent for tumor-affected vs. unaffected hemisphere – DTI: 19.46° vs. 18.99°, p=0.8931; CSD: 30.54° vs. 27.63°, p=0.0546; MLFT: 81.17° vs. 74.59°, p=0.0134). In addition, reconstructions by MLFT and CSD-based tractography nearly completely included respective bundles derived from DTI-based tractography, which was however favorable for MLFT compared to CSD-based tractography (median coverage of the DTI-based CST for affected vs. unaffected hemispheres – CSD: 68.16% vs. 77.59%, p=0.0075; MLFT: 93.09% vs. 95.49%; p=0.0046). Thus, a more complete picture of the CST in patients with motor-eloquent HGGs might be achieved based on routinely acquired diffusion MRI data using MLFT.

Outbursts of Comet 67P/Churyumov-Gerasimenko

We monitored the comet 67P/Churyumov-Gerasimenko close to its perihelion in November 2021 with the GROWTH-India Telescope. We observed two outbursts of this comet on 2021 October 29.940 and November 17.864 UTC, −3.12 days and +15.81 days respectively from the perihelion date. The brightening in the first outburst appears as a compact source, with a radial extent up to 8.″5. The comet brightened by 0.26 ± 0.03 mag in the outburst, with a 27% increase in the effective geometric cross-section and total outburst dust mass of ∼5.3 × 105 kg. The second outburst caused a brightening of 0.49 ± 0.08 mag with effective geometric cross-section and total outburst dust mass 2.5 times larger than the first event. These outbursts are up to an order of magnitude larger than the strongest outburst event observed in situ by the Rosetta spacecraft in 2015.

Wave-driven Mass Loss of Stripped Envelope Massive Stars: Progenitor-dependence, Mass Ejection, and Supernovae

The discovery of rapidly rising and fading supernovae powered by circumstellar interaction has suggested the pre-supernova mass eruption phase as a critical phenomenon in massive star evolution. It is important to understand the mass and radial extent of the circumstellar medium (CSM) from theoretically predicted mass ejection mechanisms. In this work, we study the wave heating process in massive hydrogen-poor stars, running a suite of stellar models in order to predict the wave energy and pre-explosion timescale of surface energy deposition. We survey stellar models with main-sequence progenitor masses from 20–70 M ⊙ and metallicity from 0.002–0.02. Most of these models predict that less than ∼1047 erg is deposited in the envelope, with the majority of the energy deposited in the last week of stellar evolution. This translates to CSM masses less than ∼10−2 M ⊙ that extend to less than ∼1014 cm, too small to greatly impact the light curves or spectra of the subsequent supernovae, except perhaps during the shock breakout phase. However, a few models predict somewhat higher wave energy fluxes, for which we perform hydrodynamical simulations of the mass ejection process. Radiative transfer simulations of the subsequent supernovae predict a bright but brief shock-cooling phase that could be detected in some Type Ib/c supernovae if they are discovered within a couple days of explosion.

Ten-year-and-beyond longitudinal change of ß-zone parapapillary atrophy in glaucoma: association with retinal nerve fibre layer defect

BackgroundTo investigate the longitudinal change of localised retinal nerve fibre layer (RNFL) defects associated with change of ß-zone parapapillary atrophy (PPA) in primary open-angle glaucoma (POAG) eyes.MethodsPOAG patients with a localised RNFL defect and ß-zone PPA who had undergone disc/RNFL photography at 1-year intervals for 10 years or longer were enrolled. The topographic parameters of ß-zone PPA (area, maximal radial extent and angular extent around disc) were measured. Progression of RNFL defect was defined as widening of defect and/or appearance of new defect. The factors associated with progression of RNFL defect were assessed by OR using multivariable logistic regression.ResultsA total of 209 patients (209 eyes) with POAG were included (mean: 54 years old). Over the course of 11.5±2.3-year follow-up period, progression of RNFL defect was detected in 114 eyes (54.5%). Enlargement of PPA parameters (area and angular extent) was significantly more common in patients with RNFL defect progression than in eyes without progression (all p<0.001, respectively). Widening of radial extent did not show a significant difference in both groups (p=0.61). Increment of angular extent was in the direction of RNFL defect progression in 82.1% of eyes. Progression of RNFL defect was significantly associated with disc haemorrhage (OR: 6.653, p<0.001), enlargement of PPA area (OR: 4.114, p=0.004) and angular extent (OR: 6.572, p<0.001).ConclusionsProgression of RNFL defect is associated with increment of angular extent of PPA in POAG eyes.

GOES-16 observations of rapidly-intensifying tropical cyclones: Hurricanes Harvey (2017), Maria (2017), and Michael (2018)

This study utilizes brightness temperatures (Tb’s) observed by the infrared longwave window band (Ch 14; 11.2 μm) from the Geostationary Operational Environmental Satellite-16 (GOES-16) to examine the structure of Hurricanes Harvey, Maria, and Michael throughout their lifetimes. During the times leading up to their rapid intensifications (RI), two-dimensional inner-core structures are examined to analyze the strength and location of the developing convection. Moderate vertical wind shear in the environments of Harvey and Michael induced a pronounced convective asymmetry prior to RI, followed by a rapid axisymmetrization that occurred essentially in conjunction with RI. The evolutions of the tropical cyclones’ (TCs’) coldest Tb’s indicate that the inner-core convective activity began to increase in the 12 h prior to RI onset, primarily in 2–4-h substantial “bursts”, while substantial convection dominated essentially the entirety of the region within 100 km of the surface center within 12 h of the onset of intensification.Azimuthally averaged Tb evolutions illustrate the development of each TCs’ eye and eyewall, the variability of the radial extent of the central dense overcast associated with the diurnal cycle, as well as details of the evolving convective structures throughout intensification. Hövmoller diagrams of data at constant radii reveal areas of cold Tb’s propagating around the TCs on timescales of 2–3-h. The examination of these features in a deep-layer shear-relative sense reveals that they initiate primarily downshear of the TCs’ surface centers. As RI is reached, these areas of convection are able to propagate into the upshear quadrants, which helps facilitate the onset of more substantial intensification.

Asymmetric Rainband Processes Leading to Secondary Eyewall Formation in a Model Simulation of Hurricane Matthew (2016)

The dynamics of an asymmetric rainband complex leading into secondary eyewall formation (SEF) are examined in a simulation of Hurricane Matthew (2016), with particular focus on the tangential wind field evolution. Prior to SEF, the storm experiences an axisymmetric broadening of the tangential wind field as a stationary rainband complex in the downshear quadrants intensifies. The axisymmetric acceleration pattern that causes this broadening is an inward-descending structure of positive acceleration nearly 100 km wide in radial extent and maximizes in the low levels near 50 km radius. Vertical advection from convective updrafts in the downshear-right quadrant largely contributes to the low-level acceleration maximum, while the broader inward-descending pattern is due to horizontal advection within stratiform precipitation in the downshear-left quadrant. This broad slantwise pattern of positive acceleration is due to a mesoscale descending inflow (MDI) that is driven by midlevel cooling within the stratiform regions and draws absolute angular momentum inward. The MDI is further revealed by examining the irrotational component of the radial velocity, which shows the MDI extending downwind into the upshear-left quadrant. Here, the MDI connects with the boundary layer, where new convective updrafts are triggered along its inner edge; these new upshear-left updrafts are found to be important to the subsequent axisymmetrization of the low-level tangential wind maximum within the incipient secondary eyewall.

Bushveld superplume drove Proterozoic magmatism and metallogenesis in Australia

Large-scale mantle convective processes are commonly reflected in the emplacement of Large Igneous Provinces (LIPs). These are high-volume, short-duration magmatic events consisting mainly of extensive flood basalts and their associated plumbing systems. One of the most voluminous LIPs in the geological record is the ~ 2.06 billion-year-old Bushveld Igneous Complex of South Africa (BIC), one of the most mineralised magmatic complexes on Earth. Surprisingly, the known geographic envelope of magmatism related to the BIC is limited to a series of satellite intrusions in southern Africa and has not been traced further afield. This appears inconsistent with the inferred large size of the BIC event. Here, we present new radiometric ages for alkaline magmatism in the Archean Yilgarn Craton (Western Australia), which overlap the emplacement age of the BIC and indicate a much more extensive geographic footprint of the BIC magmatic event. To assess plume involvement at this distance, we present numerical simulations of mantle plume impingement at the base of the lithosphere, and constrain a relationship between the radial extent of volcanism versus time, excess temperature and plume size. These simulations suggest that the thermal influence of large plume events could extend for thousands of km within a few million years, and produce widespread alkaline magmatism, crustal extension potentially leading to continental break-up, and large ore deposits in distal sectors. Our results imply that superplumes may produce very extensive and diverse magmatic and metallogenic provinces, which may now be preserved in widely-dispersed continental blocks.

Interplanetary Field Enhancements: An Overview

&lt;p&gt;The phenomenon, dubbed the Interplanetary Field Enhancement, occurs in the solar wind near and inside of 1 AU and is attributed to collisional dust production and subsequent solar wind pickup.&amp;#160; The duration and strength of these events appears to depend on the heliocentric distance of the detection, the largest event was recorded by the PVO spacecraft in orbit about Venus in 1982.&amp;#160; It lasted 11 hours and was over 20 million km in radial extent.&amp;#160; While no such large structure has been seen since by PVO or Venus Express since that time observations at 1 AU by STEREO, and the flotilla of spacecraft near the L-1 Lagrangian point have continued to see smaller events.&amp;#160; These are now attributed to collisions of asteroidal debris, small rocks destroying each other when they collide at a mean velocity of 20 km/s at 1 AU.&amp;#160; Such a speed of collision with a 1 kg rock will completely destroy a 10&lt;sup&gt;6&lt;/sup&gt; kg target.&amp;#160; Even if the number of small asteroids were constant with heliocentric distance the increased orbital speeds inside 1 AU should greatly increase the destructive power of collisions so that larger events should occur at closer distances to the Sun.&amp;#160; We review the statistics available from Pioneer Venus and Venus Express and compare them with 1 AU data to test this hypothesis.&lt;/p&gt;

How eigenmode self-interaction affects zonal flows and convergence of tokamak core turbulence with toroidal system size

Self-interaction is the process by which a microinstability eigenmode that is extended along the direction parallel to the magnetic field interacts non-linearly with itself. This effect is particularly significant in gyrokinetic simulations accounting for kinetic passing electron dynamics and is known to generate stationary $E\times B$ zonal flow shear layers at radial locations near low-order mode rational surfaces (Weikl et al. Phys. Plasmas, vol. 25, 2018, 072305). We find that self-interaction, in fact, plays a very significant role in also generating fluctuating zonal flows, which is critical to regulating turbulent transport throughout the radial extent. Unlike the usual picture of zonal flow drive in which microinstability eigenmodes coherently amplify the flow via modulational instabilities, the self-interaction drive of zonal flows from these eigenmodes are uncorrelated with each other. It is shown that the associated shearing rate of the fluctuating zonal flows therefore reduces as more toroidal modes are resolved in the simulation. In simulations accounting for the full toroidal domain, such an increase in the density of toroidal modes corresponds to an increase in the toroidal system size, leading to a finite system size effect that is distinct from the well-known profile shearing effect.