Using the total radiation belt electron content calculated from Van Allen Probe phase space density, the time‐dependent and global response of the outer radiation belt during storms is statistically ...studied. Using phase space density reduces the impacts of adiabatic changes in the main phase, allowing a separation of adiabatic and nonadiabatic effects and revealing a clear modality and repeatable sequence of events in storm time radiation belt electron dynamics. This sequence exhibits an important first adiabatic invariant (μ)‐dependent behavior in the seed (150 MeV/G), relativistic (1,000 MeV/G), and ultrarelativistic (4,000 MeV/G) populations. The outer radiation belt statistically shows an initial phase dominated by loss followed by a second phase of rapid acceleration, while the seed population shows little loss and immediate enhancement. The time sequence of the transition to the acceleration is also strongly μ dependent and occurs at low μ first, appearing to be repeatable from storm to storm.
Plain Language Summary
The Earth's outer radiation belt is a region of near‐Earth space composed of highly energetic electrons. Typically, the outer radiation belt is in a quiet state; however, during geomagnetic storms the outer radiation belt becomes extremely dynamic. During these storms rapid changes in the number of energetic electrons in the outer radiation belt can lead to satellite failures. Our new research has found a level repeatability in storm time outer radiation belt dynamics not previously appreciated and offers important insights into radiation belt modeling and forecasting. This new work can be used to mitigate the negative effects radiation belt electrons can have on satellite infrastructure.
Key Points
Statistical assessment of the global and repeatable response of the outer radiation belt to storms
Using radiation belt content derived from phase space density reduces impacts from adiabatic changes revealing a clear sequence of events
The statistical response is characterized by a fast genuine‐loss dominated phase followed by a clear acceleration phase
The sequence of events associated with the triggering of energy release during substorm expansion phase onset is still not well‐understood. Oberhagemann and Mann (2020b, ...https://doi.org/10.1029/2019gl085271) proposed a new substorm onset mechanism, where the transition toward parallel proton pressure anisotropy during tail stretching in the late growth phase could trigger a pressure anisotropic ballooning instability. Here we examine the evolution of energetic proton parallel pressure anisotropy at geosynchronous altitudes, seeking evidence in support of the proposed substorm onset mechanism. We use the Geostationary Operational Environment Satellite (GOES) proton flux and magnetometer data combined with substorm onset indicators derived from ground‐based magnetometers. Superposed epoch analysis of substorm onset times for 2014 using the isolated substorm list (Ohtani & Gjerloev, 2020, https://doi.org/10.1029/2020ja027902) clearly shows signatures of energetic proton parallel pressure anisotropy immediately before substorm onset, potentially supportive of the Oberhagemann and Mann theory.
Plain Language Summary
Substorms are disturbances in the nightside region of the geospace associated with the rapid release of stored magnetic energy. In the ionosphere, the signatures of this energy release are the spectacular dancing lights known as aurorae (northern and southern lights). The processes that lead to energy storage are well‐known. However, there are competing theories on what triggers the release of this significant amount of energy at substorm onset. According to a new substorm onset theory proposed by Oberhagemann and Mann, when the magnetic field stretches in the nightside during the energy storage, the pressure becomes more parallel to the magnetic field, leading to a ballooning instability at substorm onset. Here, we look for observational support for the association of such pressure profile at geosynchronous altitudes with substorm onset to examine the proposed model. Superposed epoch analysis of isolated substorms in 2014 shows increasing energetic proton parallel pressure anisotropy at the onset, providing evidence to support the Oberhagemann and Mann theory.
Key Points
Oberhagemann and Mann theory proposes that proton parallel temperature anisotropy triggers ballooning instability leading to substorm onset
We use pitch angle resolved energetic proton fluxes at geosynchronous altitudes seeking observational evidence in support of the model
Superposed epoch analysis of isolated substorms shows signatures of increasing energetic proton parallel anisotropy which peaks near onset
A
bstract
We consider a conformal complex singlet extension of the Standard Model with a Higgs portal interaction. The global U(1) symmetry of the complex singlet can be either broken or unbroken and ...we study each scenario. In the unbroken case, the global U(1) symmetry protects the complex singlet from decaying, leading to an ideal cold dark matter candidate with approximately 100 GeV mass along with a significant proportion of thermal relic dark matter abundance. In the broken case, we have developed a renormalization-scale optimization technique to significantly narrow the parameter space and in some situations, provide unique predictions for all the model’s couplings and masses. We have found there exists a second Higgs boson with a mass of approximately 550 GeV that mixes with the known 125 GeV Higgs with a large mixing angle sin
θ
≈ 0.47 consistent with current experimental limits. The imaginary part of the complex singlet in the broken case could provide axion dark matter for a wide range of models. Upon including interactions of the complex scalar with an additional vector-like fermion, we explore the possibility of a diphoton excess in both the unbroken and the broken cases. In the unbroken case, the model can provide a natural explanation for diphoton excess if extra terms are introduced providing extra contributions to the singlet mass. In the broken case, we find a set of coupling solutions that yield a second Higgs boson of mass 720 GeV and an 830 GeV extra vector-like fermion
F
, which is able to address the 750 GeV LHC diphoton excess. We also provide criteria to determine the symmetry breaking pattern in both the Higgs and hidden sectors.
Context. Cassiopeia A is one of the best-studied supernova remnants. Its bright radio and X-ray emission is due to shocked ejecta. Cas A is rather unique in that the unshocked ejecta can also be ...studied: through emission in the infrared, the radio-active decay of 44Ti, and the low-frequency free-free absorption caused by cold ionised gas, which is the topic of this paper. Aims. Free-free absorption processes are affected by the mass, geometry, temperature, and ionisation conditions in the absorbing gas. Observations at the lowest radio frequencies can constrain a combination of these properties. Methods. We used Low Frequency Array (LOFAR) Low Band Antenna observations at 30–77 MHz and Very Large Array (VLA) L-band observations at 1–2 GHz to fit for internal absorption as parametrised by the emission measure. We simultaneously fit multiple UV-matched images with a common resolution of 17″ (this corresponds to 0.25 pc for a source at the distance of Cas A). The ample frequency coverage allows us separate the relative contributions from the absorbing gas, the unabsorbed front of the shell, and the absorbed back of the shell to the emission spectrum. We explored the effects that a temperature lower than the ~100–500 K proposed from infrared observations and a high degree of clumping can have on the derived physical properties of the unshocked material, such as its mass and density. We also compiled integrated radio flux density measurements, fit for the absorption processes that occur in the radio band, and considered their effect on the secular decline of the source. Results. We find a mass in the unshocked ejecta of M = 2.95 ± 0.48 M⊙ for an assumed gas temperatureof T = 100 K. This estimate is reduced for colder gas temperatures and, most significantly, if the ejecta are clumped. We measure the reverse shock to have a radius of 114″± 6″ and be centred at 23:23:26, +58:48:54 (J2000). We also find that a decrease in the amount of mass in the unshocked ejecta (as more and more material meets the reverse shock and heats up) cannot account for the observed low-frequency behaviour of the secular decline rate. Conclusions. To reconcile our low-frequency absorption measurements with models that reproduce much of the observed behaviour in Cas A and predict little mass in the unshocked ejecta, the ejecta need to be very clumped or the temperature in the cold gas needs to be low (~10 K). Both of these options are plausible and can together contribute to the high absorption value that we find.
We reviewed 140 papers to assess the ecological effectiveness of South Africa's marine protected areas (MPAs). Evidence was assessed for coverage and representivity, protection of important ...biodiversity areas, other recognised elements of effectiveness, connectivity, and ecological effects-from the scale of individual MPAs to the MPA network scale. We conducted complementary novel analyses to supplement the review and to objectively determine where and how the MPA network can be improved. Evidence shows that South Africa's MPAs now provide some protection to all ecoregions and 87% of ecosystem types but to less than 50% of assessed species groups. MPAs are generally well-sited, but gaps were revealed on the west coast and in estuaries, the deep sea, and two ecologically and biologically significant areas. Enforcement emerged as a key concern, and many MPAs could be improved through expansion or by increasing no-take areas. The majority of relevant papers recorded beneficial ecological effects, detectable as increases in parameters such as the abundance, biomass, sizes or reproductive output of species. Few papers examined whether ecological benefits translate into adjacent fisheries benefits, but all those that did recorded positive effects. Full protection was more effective than partial protection, with effectiveness most clearly demonstrated for vulnerable target taxa. Further research and monitoring to achieve evaluations of effectiveness are recommended, with greater focus on neglected MPAs and species. Understanding the ecological connectivity between MPAs, an important dimension for climate-change adaptation and hence for the persistence and resilience of South Africa's marine biodiversity, is identified as a key area for future research and inclusion in MPA planning.
Malignant peritoneal mesothelioma in childhood Armstrong, G R; Raafat, F; Ingram, L ...
Archives of pathology & laboratory medicine (1976),
11/1988, Letnik:
112, Številka:
11
Journal Article
Recenzirano
We present a case of diffuse malignant peritoneal mesothelioma, initially misdiagnosed as benign. Electron microscopy and immunocytochemistry proved helpful diagnostically. Using monoclonal ...antibodies against cytokeratin and vimentin, we compared neoplastic with normal and reactive mesothelia and we found coexpression of these two intermediate filaments in the reactive and neoplastic mesothelial but not in the normal mesothelia, supporting the suggestion that surface mesothelial cells are derived from multipotential submesothelial cells.
LOFAR: The LOw-Frequency ARray Wise, M. W.; Gunst, A. W.; Heald, G. ...
Astronomy and astrophysics (Berlin),
08/2013, Letnik:
556
Journal Article
Recenzirano
Odprti dostop
LOFAR, the LOw-Frequency ARray, is a new-generation radio interferometer constructed in the north of the Netherlands and across europe. Utilizing a novel phased-array design, LOFAR covers the largely ...unexplored low-frequency range from 10–240 MHz and provides a number of unique observing capabilities. Spreading out from a core located near the village of Exloo in the northeast of the Netherlands, a total of 40 LOFAR stations are nearing completion. A further five stations have been deployed throughout Germany, and one station has been built in each of France, Sweden, and the UK. Digital beam-forming techniques make the LOFAR system agile and allow for rapid repointing of the telescope as well as the potential for multiple simultaneous observations. With its dense core array and long interferometric baselines, LOFAR achieves unparalleled sensitivity and angular resolution in the low-frequency radio regime. The LOFAR facilities are jointly operated by the International LOFAR Telescope (ILT) foundation, as an observatory open to the global astronomical community. LOFAR is one of the first radio observatories to feature automated processing pipelines to deliver fully calibrated science products to its user community. LOFAR’s new capabilities, techniques and modus operandi make it an important pathfinder for the Square Kilometre Array (SKA). We give an overview of the LOFAR instrument, its major hardware and software components, and the core science objectives that have driven its design. In addition, we present a selection of new results from the commissioning phase of this new radio observatory.
Objective
Mood disorders are strongly associated with suicide, the prevention of which is predicated on timely detection of suicidal activity (ideation, behaviour). Building on our previous work, we ...sought to determine the nature of neural responses to an emotional‐cognitive task in patients with varying degrees of suicidal activity.
Method
Seventy‐nine patients with mood disorders were assessed clinically and scanned using fMRI. Neural responses to an Emotional Face‐Word Stroop task were compared with 66 healthy controls. We identified regions of interest from seven key networks and examined responses to incongruent stimuli (Happy face‐‘Sad’ word; Sad face‐‘Happy’ word).
Results
In comparison with healthy controls, patients had differential activity during both incongruent conditions. When examining for associations with suicidal activity within the patient group, those with higher scores had decreased default mode network activity for Happy face‐‘Sad’ word manipulation, and increased basal ganglia network activity for Sad face‐‘Happy’ word manipulation, after controlling for patient characteristics.
Conclusion
The fMRI findings suggest that suicidal activity in patients with mood disorders may be underpinned by cognitive–emotional deficits. These findings have implications for future suicide research and for achieving a deeper understanding of suicidal activity that may ultimately inform clinical detection and management.
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