Context.
Despite over 50 years of research, many open questions remain about the origin and nature of gamma-ray bursts (GRBs). Linear polarization measurements of the prompt emission of these extreme ...phenomena have long been thought to be key to answering a range of these questions. The POLAR detector was designed to produce the first set of detailed and reliable linear polarization measurements in the 50 − 500 keV energy range. During late 2016 and early 2017, POLAR detected a total of 55 GRBs. The analysis results of 5 of these GRBs have been reported, and were found to be consistent with a low or unpolarized flux. However, previous reports by other collaborations found high levels of linear polarization, including some as high as 90%.
Aims.
We study the linear polarization for the 14 GRBs observed by POLAR for which statistically robust inferences are possible. Additionally, time-resolved polarization studies are performed on GRBs with sufficient apparent flux.
Methods.
A publicly available polarization analysis tool, developed within the Multi-Mission Maximum Likelihood framework (
3ML
), was used to produce statistically robust results. The method allows spectral and polarimetric data from POLAR to be combined with spectral data from the
Fermi
Gamma-ray Burst Monitor (
Fermi
-GBM) and the
Neil Gehrels Swift
Observatory to jointly model the spectral and polarimetric parameters.
Results.
The time-integrated analysis finds all results to be compatible with low or zero polarization with the caveat that, when time-resolved analysis is possible within individual pulses, we observe moderate linear polarization with a rapidly changing polarization angle. Therefore, time-integrated polarization results, while pointing to lower polarization, are potentially an artifact of summing over the changing polarization signal and thus washing out the true moderate polarization. We therefore caution against overinterpretation of any time-integrated results inferred herein and encourage the community to wait for more detailed polarization measurements from forthcoming missions such as POLAR-2 and LEAP.
In neuroscience, empathy is often conceived as relatively automatic. The voluntary control that people can exert on brain mechanisms that map the emotions of others onto our own emotions has received ...comparatively less attention. Here, we therefore measured brain activity while participants watched emotional Hollywood movies under two different instructions: to rate the main characters’ emotions by empathizing with them, or to do so while keeping a detached perspective. We found that participants yielded highly consistent and similar ratings of emotions under both conditions. Using intersubject correlation-based analyses we found that, when encouraged to empathize, participants’ brain activity in limbic (including cingulate and putamen) and somatomotor regions (including premotor, SI and SII) synchronized more during the movie than when encouraged to detach. Using intersubject functional connectivity we found that comparing the empathic and detached perspectives revealed widespread increases in functional connectivity between large scale networks. Our findings contribute to the increasing awareness that we have voluntary control over the neural mechanisms through which we process the emotions of others.
•People are highly consistent in their rating of characters’ emotions in movies.•Voluntarily empathizing increases recruitment of empathy related brain regions.•Voluntarily empathizing increases functional connectivity across networks.•Voluntarily empathizing increases perceived intensity of other people’s emotions.
Advanced composite materials are finding increasing application in aerospace, marine and many other industries due to their performance and structural efficiency. Maintenance inspection of these ...light-weight structures is a relatively new and difficult task for Non-Destructive Testing (NDT), which need robust methods to be applicable in industrial environments. In this paper, a new numerical–experimental procedure to detect size and depth of flat bottom holes in metallic and laminated composite structures by digital shearography (DISH) is proposed. The flaw detection capabilities of DISH have been evaluated by measuring the dynamic response of defects to applied stresses. Vibration dynamic loading is used to reveal flat bottom holes made with different sizes and placed at different depths in CFRP laminates. The shearographic methodology is based on the recognition of the (0 1) resonance mode per defect. A simplified model of thin circular plate, idealized above each flaw position, is used to calculate the natural frequency of vibrating defects. Then, the numerical difference between experimental resonance frequencies and those computationally obtained is minimized using an unconstrained optimization algorithm in order to calculate the defect depth. Considering the simplicity and rapidity of this technique, the laser shearography methodology is evaluated reliable as NDT method.
► We proposed a simple method to detect impact damage in composite structures. ► It uses a combination of shearography and optimization methods. ► Demonstrated a good accuracy in locating and sizing delaminations areas and depth.
Serous cystic neoplasm (SCN) is a cystic neoplasm of the pancreas whose natural history is poorly known. The purpose of the study was to attempt to describe the natural history of SCN, including the ...specific mortality.
Retrospective multinational study including SCN diagnosed between 1990 and 2014.
2622 patients were included. Seventy-four per cent were women, and median age at diagnosis was 58 years (16-99). Patients presented with non-specific abdominal pain (27%), pancreaticobiliary symptoms (9%), diabetes mellitus (5%), other symptoms (4%) and/or were asymptomatic (61%). Fifty-two per cent of patients were operated on during the first year after diagnosis (median size: 40 mm (2-200)), 9% had resection beyond 1 year of follow-up (3 years (1-20), size at diagnosis: 25 mm (4-140)) and 39% had no surgery (3.6 years (1-23), 25.5 mm (1-200)). Surgical indications were (not exclusive) uncertain diagnosis (60%), symptoms (23%), size increase (12%), large size (6%) and adjacent organ compression (5%). In patients followed beyond 1 year (n=1271), size increased in 37% (growth rate: 4 mm/year), was stable in 57% and decreased in 6%. Three serous cystadenocarcinomas were recorded. Postoperative mortality was 0.6% (n=10), and SCN's related mortality was 0.1% (n=1).
After a 3-year follow-up, clinical relevant symptoms occurred in a very small proportion of patients and size slowly increased in less than half. Surgical treatment should be proposed only for diagnosis remaining uncertain after complete workup, significant and related symptoms or exceptionally when exists concern with malignancy. This study supports an initial conservative management in the majority of patients with SCN.
IRB 00006477.
Extensive deposits of methane hydrate characterize Hydrate Ridge in the Cascadia margin accretionary complex. The ridge has a northern peak at a depth of about 600 m, which is covered by extensive ...carbonate deposits, and an 800 m deep southern peak that is predominantly sediment covered. Samples collected with benthic instrumentation and from
Alvin push cores reveal a complex hydrogeologic system where fluid and methane fluxes from the seafloor vary by several orders of magnitude at sites separated by distances of only a few meters. We identified three distinct active fluid regimes at Hydrate Ridge. The first province is represented by discrete sites of methane gas ebullition, where the bulk of the flow occurs through channels in which gas velocities reach 1 m s
−1. At the northern summit of the ridge the gas discharge appears to be driven by pressure changes on a deep gas reservoir, and it is released episodically at a rate of ∼6×10
4 mol day
−1 following tidal periodicity. Qualitative observations at the southern peak suggest that the gas discharge there is driven by more localized phenomena, possibly associated with destabilization of massive gas hydrate deposits at the seafloor. The second province is characterized by the presence of extensive bacterial mats that overlay sediments capped with methane hydrate crusts, both at the northern and southern summits. Here fluid typically flows out of the sediments at rates ranging from 30 to 100 cm yr
−1. The third province is represented by sites colonized by vesicomyid clams, where bottom seawater flows into the sediments for at least some fraction of the time. Away from the active gas release sites, fluid flows calculated from pore water models are in agreement with estimates using published flowmeter data and numerical model calculations. Methane fluxes out of mat-covered sites range from 30 to 90 mmol m
−2 day
−1, whereas at clam sites the methane flux is less than 1 mmol m
−2 day
−1.
Microquasars are binary star systems with relativistic radio-emitting jets. They are potential sources of cosmic rays and can be used to elucidate the physics of relativistic jets. We report the ...detection of variable gamma-ray emission above 100 gigaelectron volts from the microquasar LS I 61 + 303. Six orbital cycles were recorded. Several detections occur at a similar orbital phase, which suggests that the emission is periodic. The strongest gamma-ray emission is not observed when the two stars are closest to one another, implying a strong orbital modulation of the emission or absorption processes.
The atmospheric Cherenkov gamma-ray telescope MAGIC, designed for a low-energy threshold, has detected very-high-energy gamma rays from a giant flare of the distant Quasi-Stellar Radio Source (in ...short: radio quasar) 3C 279, at a distance of more than 5 billion light-years (a redshift of 0.536). No quasar has been observed previously in very-high-energy gamma radiation, and this is also the most distant object detected emitting gamma rays above 50 gigaelectron volts. Because high-energy gamma rays may be stopped by interacting with the diffuse background light in the universe, the observations by MAGIC imply a low amount for such light, consistent with that known from galaxy counts.
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