Effects of Respiratory Motion on Y-90 PET Dosimetry for SIRT

Respiratory motion degrades the quantification accuracy of PET imaging by blurring the radioactivity distribution. In the case of post-SIRT PET-CT verification imaging, respiratory motion can lead to inaccuracies in dosimetric measures. Using an anthropomorphic phantom filled with 90Y at a range of clinically relevant activities, together with a respiratory motion platform performing realistic motions (10–15 mm amplitude), we assessed the impact of respiratory motion on PET-derived post-SIRT dosimetry. Two PET scanners at two sites were included in the assessment. The phantom experiments showed that device-driven quiescent period respiratory motion correction improved the accuracy of the quantification with statistically significant increases in both the mean contrast recovery (+5%, p = 0.003) and the threshold activities corresponding to the dose to 80% of the volume of interest (+6%, p < 0.001). Although quiescent period gating also reduces the number of counts and hence increases the noise in the PET image, its use is encouraged where accurate quantification of the above metrics is desired.

A transient postnatal quiescent period precedes emergence of mature cortical dynamics

Mature neural networks synchronize and integrate spatiotemporal activity patterns to support cognition. Emergence of these activity patterns and functions is believed to be developmentally regulated, but the postnatal time course for neural networks to perform complex computations remains unknown. We investigate the progression of large-scale synaptic and cellular activity patterns across development using high spatiotemporal resolution in vivo electrophysiology in immature mice. We reveal that mature cortical processes emerge rapidly and simultaneously after a discrete but volatile transition period at the beginning of the second postnatal week of rodent development. The transition is characterized by relative neural quiescence, after which spatially distributed, temporally precise, and internally organized activity occurs. We demonstrate a similar developmental trajectory in humans, suggesting an evolutionarily conserved mechanism that could facilitate a transition in network operation. We hypothesize that this transient quiescent period is a requisite for the subsequent emergence of coordinated cortical networks.

Sexual behaviour of the blister beetle Epicauta atomaria (Germar), with remarks on the bionomics of Epicauta maculata species group (Meloidae: Meloinae: Epicautini)

The sexual behaviour of the blister beetle Epicauta atomaria (Germar) (Meloidae: Meloinae: Epicautini), a pest that affects diverse crops of economic importance in South America, was evaluated for the first time under laboratory conditions. Twelve pairs of E. atomaria adults were collected from low-lying roadsides adjacent to grazed areas in Diamante, Entre Ríos, Argentina. To describe the sexual behaviour of this species, the number of events and their duration within different courtship phases in E. atomaria males were compared. An ethogram was built, showing that males perform three different behaviours during courtship phases: the quiescent period, antennal rubbing, and mounting. Our results showed that, during courtship, the number of events and the time of the mounting were low and significantly lower compared to behaviours undertaken during the quiescent period and antennal rubbing. In conclusion, the courtship of E. atomaria was clearly dominated by the quiescent period and antennal rubbing. To date, this is the first study to investigate sexual behaviour in E. atomaria, providing a foundation for future phylogenetic studies.

A transient postnatal quiescent period precedes emergence of mature cortical dynamics

Mature neural networks synchronize and integrate spatiotemporal activity patterns to support cognition. Emergence of these activity patterns and functions is believed to be developmentally regulated, but the postnatal time course for neural networks to perform complex computations remains unknown. We investigate the progression of large-scale synaptic and cellular activity patterns across development using high spatiotemporal resolution in vivo electrophysiology in immature mice. We reveal that mature cortical processes emerge rapidly and simultaneously after a discrete but volatile transition period at the beginning of the second postnatal week of rodent development. The transition is characterized by relative neural quiescence, after which spatially distributed, temporally precise, and internally organized activity occurs. We demonstrate a similar developmental trajectory in humans, suggesting an evolutionarily conserved mechanism to transition network operation. We hypothesize that this transient quiescent period is a requisite for the subsequent emergence of coordinated cortical networks.

Evaluation of a method for converting Stratospheric Aerosol and Gas Experiment (SAGE) extinction coefficients to backscatter coefficients for intercomparison with lidar observations

Aerosol backscatter coefficients were calculated using multiwavelength aerosol extinction products from the SAGE II and III/ISS instruments (SAGE: Stratospheric Aerosol and Gas Experiment). The conversion methodology is presented, followed by an evaluation of the conversion algorithm's robustness. The SAGE-based backscatter products were compared to backscatter coefficients derived from ground-based lidar at three sites (Table Mountain Facility, Mauna Loa, and Observatoire de Haute-Provence). Further, the SAGE-derived lidar ratios were compared to values from previous balloon and theoretical studies. This evaluation includes the major eruption of Mt. Pinatubo in 1991, followed by the atmospherically quiescent period beginning in the late 1990s. Recommendations are made regarding the use of this method for evaluation of aerosol extinction profiles collected using the occultation method.

How unusual is the Milky Way’s assembly history?

ABSTRACT In the lambda cold dark matter (ΛCDM) model of structure formation galactic haloes build-up by accretion of mass and mergers of smaller haloes. The most recent massive merger event experienced by the Milky Way (MW) halo was the accretion of the Large Magellanic Cloud (LMC; which has a stellar mass of ∼109M⊙). Recent analyses of galactic stellar data from the Gaia satellite have uncovered an earlier massive accretion event, the Gaia-Enceladus Sausage (GES), which merged with the MW around 10 Gyr ago. Here, we use the EAGLE cosmological hydrodynamics simulation to study properties of simulated MW-mass haloes constrained to have accretion histories similar to that of the MW, specifically the recent accretion of an ‘LMC’ galaxy and a ‘GES’ merger, with a quiescent period between the GES merger and the infall of the LMC (the ‘LMC and GES’ category). We find that ∼16 per cent of MW-mass haloes have an LMC; ∼5 per cent have a GES event and no further merger with an equally massive object since z = 1; and only 0.65 per cent belong to the LMC and GES category. The progenitors of the MWs in this last category are much less massive than average at early times but eventually catch up with the mean. The LMC and GES category of galaxies naturally end up in the ‘blue cloud’ in the colour–magnitude diagram at z = 0, tend to have a disc morphology and have a larger than average number of satellite galaxies.

Long-term (1999–2019) variability of stratospheric aerosol over Mauna Loa, Hawaii, as seen by two co-located lidars and satellite measurements

As part of the Network for the Detection of Atmospheric Composition Change (NDACC), ground-based measurements obtained from the Jet Propulsion Laboratory (JPL) stratospheric ozone lidar and the NOAA stratospheric aerosol lidar at Mauna Loa, Hawaii, over the past 2 decades were used to investigate the impact of volcanic eruptions and pyrocumulonimbus (PyroCb) smoke plumes on the stratospheric aerosol load above Hawaii since 1999. Measurements at 355 and 532 nm conducted by these two lidars revealed a color ratio of 0.5 for background aerosols and small volcanic plumes and 0.8 for a PyroCb plume recorded on September 2017. Measurements of the Nabro plume by the JPL lidar in 2011–2012 showed a lidar ratio of (64±12.7) sr at 355 nm around the center of the plume. The new Global Space-based Stratospheric Aerosol Climatology (GloSSAC), Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) Level 3 and Stratospheric Aerosol and Gas Experiment III on the International Space Station (SAGE III-ISS) stratospheric aerosol datasets were compared to the ground-based lidar datasets. The intercomparison revealed a generally good agreement, with vertical profiles of extinction coefficient within 50 % discrepancy between 17 and 23 km above sea level (a.s.l.) and 25 % above 23 km a.s.l. The stratospheric aerosol depth derived from all of these datasets shows good agreement, with the largest discrepancy (20 %) being observed between the new CALIOP Level 3 and the other datasets. All datasets consistently reveal a relatively quiescent period between 1999 and 2006, followed by an active period of multiple eruptions (e.g., Nabro) until early 2012. Another quiescent period, with slightly higher aerosol background, lasted until mid-2017, when a combination of extensive wildfires and multiple volcanic eruptions caused a significant increase in stratospheric aerosol loading. This loading maximized at the very end of the time period considered (fall 2019) as a result of the Raikoke eruption, the plume of which ascended to 26 km altitude in less than 3 months.

Seismic Scatter Associated with Earthquakes that Ended a Quiescent Period in Southeastern Korea

Two recent hazardous earthquakes ( M 5.8 and 5.5) in southeastern Korea were the largest instrumentally recorded inland events after an abnormally long, seismically quiet, period. In this study, we used coda envelope tomography to observe the heterogeneities related to active faults, which can, in turn, help mitigate seismic hazard in the area. However, this tomography was not able to detect faults in the intraplate region. By separating the periods before and after the M 5.8 earthquake, we analyzed 225 and 204 seismograms obtained from 127 and 86 events, respectively. Both periods showed time-varying heterogeneity correlated with fault activity. Adding 446 seismograms from 235 aftershocks of the two events to the analysis showed us a heterogenous structure that closely correlated to the active faults where the recent earthquakes originated.

Long-term (1999–2019) variability of stratospheric aerosol over Mauna Loa, Hawaii, as seen by two co-located lidars and satellite measurements

As part of the Network for the Detection of Atmospheric Composition Change (NDACC), ground-based measurements obtained from the Jet Propulsion Laboratory (JPL) stratospheric ozone lidar and the NOAA stratospheric aerosol lidar at Mauna Loa, Hawaii over the past two decades were used to investigate the impact of volcanic eruptions and pyro-cumulonimbus smoke plumes on the stratospheric aerosol load above Hawaii since 1999. Measurements at 355 nm and 532 nm conducted by these two lidars revealed Ångström exponents of −1.6 for background plumes and −0.6 for a PyroCb plume recorded on September 2017. Measurements of the Nabro plume by the JPL lidar in 2011/2012 showed a lidar ratio of (64 ± 12.7) sr at 355 nm around the center of the plume. The new GloSSAC, CALIOP Level 3 and SAGE III-ISS stratospheric aerosol datasets were compared to the ground-based lidar datasets. The intercomparison revealed a generally good agreement, with vertical profiles of extinction coefficient within 50 % of discrepancy between 17 km and 23 km above sea level (ASL), and 25 % above 23 km ASL. The stratospheric aerosol depth derived from all these datasets shows good agreement, with the largest discrepancy (20 %) being observed between the new CALIOP Level 3 and the other datasets. All datasets consistently reveal a relatively quiescent period between 1999 and 2005, followed by an active period of multiple eruptions (e.g., Nabro) until early 2012. Another quiescent period, with slightly higher aerosol background, lasted until mid-2017, when a combination of extensive wildfires and multiple volcanic eruptions caused a significant increase in stratospheric aerosol loading. This loading maximized at the very end of the time period considered (fall 2019) as a result of the Raikoke eruption, the plume of which ascended to 26 km altitude in less than three months.

Pore Water Pressure Response of Fully Saturated Soil Beds during Earthquake–Tsunami Multi‐Hazards

Soil liquefaction causes significant damage to coastal infrastructure and buildings worldwide. Strong earthquake shaking can cause soil liquefaction in fully saturated sand deposits. Also, tsunamis can induce liquefaction, as well as enhanced sediment transport and scour, in coastal areas. To understand soil liquefaction potential during an earthquake–tsunami multi‐hazard, we develop a numerical model to predict the multi‐hazard induced excess pore water pressures. We calibrate and verify the numerical model by comparing results with laboratory experiments. Then, we perform numerical experiments using a recorded earthquake motion and hypothetical tsunami wave heights. The numerical experiments show that beach sand liquefies during earthquake loading. The sand then resediments during the quiescent period and the tsunami runup stage. Finally, during rapid tsunami drawdown, liquefaction can occur again, and liquefaction potential during tsunami drawdown primarily depends on the soil’s hydraulic conductivity, as well as the duration of the quiescent period. The results emphasize the need for predictions of earthquake–tsunami loading, as well as measurements of soil properties in coastal areas.