605 research outputs found
Rotation-supported Neutrino-driven Supernova Explosions in Three Dimensions and the Critical Luminosity Condition
We present the first self-consistent, three-dimensional (3D) core-collapse
supernova simulations performed with the Prometheus-Vertex code for a rotating
progenitor star. Besides using the angular momentum of the 15 solar-mass model
as obtained in the stellar evolution calculation with an angular frequency of
about 0.001 rad/s (spin period of more than 6000 s) at the Si/Si-O interface,
we also computed 2D and 3D cases with no rotation and with a ~300 times shorter
rotation period and different angular resolutions. In 2D, only the nonrotating
and slowly rotating models explode, while rapid rotation prevents an explosion
within 500 ms after bounce because of lower radiated neutrino luminosities and
mean energies and thus reduced neutrino heating. In contrast, only the fast
rotating model develops an explosion in 3D when the Si/Si-O interface collapses
through the shock. The explosion becomes possible by the support of a powerful
SASI spiral mode, which compensates for the reduced neutrino heating and pushes
strong shock expansion in the equatorial plane. Fast rotation in 3D leads to a
"two-dimensionalization" of the turbulent energy spectrum (yielding roughly a
-3 instead of a -5/3 power-law slope at intermediate wavelengths) with enhanced
kinetic energy on the largest spatial scales. We also introduce a
generalization of the "universal critical luminosity condition" of Summa et al.
(2016) to account for the effects of rotation, and demonstrate its viability
for a set of more than 40 core-collapse simulations including 9 and 20
solar-mass progenitors as well as black-hole forming cases of 40 and 75
solar-mass stars to be discussed in forthcoming papers.Comment: 24 pages, 19 figures; refereed version with additional section on
resolution dependence; accepted by Ap
Gravitational waves from three-dimensional core-collapse supernova models: The impact of moderate progenitor rotation
We present predictions for the gravitational-wave (GW) emission of
three-dimensional supernova (SN) simulations performed for a 15 solar-mass
progenitor with the Prometheus-Vertex code using energy-dependent, three-flavor
neutrino transport. The progenitor adopted from stellar evolution calculations
including magnetic fields had a fairly low specific angular momentum (j_Fe <~
10^{15} cm^2/s) in the iron core (central angular velocity ~0.2 rad/s), which
we compared to simulations without rotation and with artificially enhanced
rotation (j_Fe <~ 2*10^{16} cm^2/s; central angular velocity ~0.5 rad/s). Our
results confirm that the time-domain GW signals of SNe are stochastic, but
possess deterministic components with characteristic patterns at low
frequencies (<~200 Hz), caused by mass motions due to the standing accretion
shock instability (SASI), and at high frequencies, associated with gravity-mode
oscillations in the surface layer of the proto-neutron star (PNS). Non-radial
mass motions in the post-shock layer as well as PNS convection are important
triggers of GW emission, whose amplitude scales with the power of the
hydrodynamic flows. There is no monotonic increase of the GW amplitude with
rotation, but a clear correlation with the strength of SASI activity. Our
slowly rotating model is a fainter GW emitter than the non-rotating model
because of weaker SASI activity and damped convection in the post-shock layer
and PNS. In contrast, the faster rotating model exhibits a powerful SASI spiral
mode during its transition to explosion, producing the highest GW amplitudes
with a distinctive drift of the low-frequency emission peak from ~80-100 Hz to
~40-50 Hz. This migration signifies shock expansion, whereas non-exploding
models are discriminated by the opposite trend.Comment: Added new figure, figure 9. Updated figure 9, now figure 10. Modified
the discussion of the proto-neutron star convection. Added a figure showing
the average rotation rate as a function of radius. Added a section discussing
where the low-frequency gravitational waves are generated, this information
is visualized in figure 9. We also made some minor changes to the text and
selected plot
Migration and Intra-Urban Residential Mobility in the Helsinki Metropolitan Area
This paper was contributed to IIASA's workshop on "Dynamics of Metropolitan Areas" in Rotterdam, June 1984. It contains an assessment of migration process in the Helsinki region and examines in particular age-dependent mobility of life-cycle type. As such it also provides a background to the study on housing dynamics in the Helsinki region
Clear-air lidar dark band
This paper illustrates measurements carried out by the Raman lidar BASIL in the frame of HOPE, revealing the presence of a clear-air dark band phenomenon (i.e. the appearance of a minimum in lidar backscatter echoes) in the upper portion of the convective boundary layer. The phenomenon is clearly distinguishable in the lidar backscatter echoes at 1064 nm. This phenomenon is attributed to the presence of lignite aerosol particles advected from the surrounding open pit mines in the vicinity of the measuring site
Thermal and Cold Neutron Computed Tomography at the Los Alamos Neutron Scattering Center Using an Amorphous Silicon Detector Array
The use of the EG&G-Heimann RTM 128 [1] or dpiX FS20 [2] amorphous silicon (a-Si) detector array for thermal neutron radiography/computed tomography has proven to be a quick and efficient means of producing high quality digital radiographic images. The resolution, although not as good as film, is about 750 μm with the RTM and 127 μm with the dpiX array with a dynamic range in excess of 2800. In many respects using an amorphous silicon detector is an improvement over other techniques such as imaging with a CCD camera, using a storage phosphor plate or film radiography. Unlike a CCD camera, which is highly susceptible to radiation damage, a-Si detectors can be placed in the beam directly behind the object under examination and do not require any special optics or turning mirrors. The amorphous silicon detector also allows enough data to be acquired to construct a digital image in just a few seconds (minimum gate time 40 ms) whereas film or storage plate exposures can take many minutes and need to be digitized with a scanner. The flat panel can, therefore, acquire a complete 3D computed tomography data set in just a few tens of minutes. While a-Si detectors have been proposed for use in imaging neutron beams [3], this is the first reported implementation of such a detector for neutron imaging [4]
Neutrophils, Crucial, or Harmful Immune Cells Involved in Coronavirus Infection: A Bioinformatics Study
The latest member of the Coronaviridae family, called SARS-CoV-2, causes the Coronavirus Disease 2019 (COVID-19). The disease has caused a pandemic and is threatening global health. Similar to SARS-CoV, this new virus can potentially infect lower respiratory tract cells and can go on to cause severe acute respiratory tract syndrome, followed by pneumonia and even death in many nations. The molecular mechanism of the disease has not yet been evaluated until now. We analyzed the GSE1739 microarray dataset including 10 SARS-positive PBMC and four normal PBMC. Co-expression network analysis by WGCNA suggested that highly preserved 833 turquoise module with genes were significantly related to SARS-CoV infection. ELANE, ORM2, RETN, BPI, ARG1, DEFA4, CXCL1, and CAMP were the most important genes involved in this disease according to GEO2R analysis as well. The GO analysis demonstrated that neutrophil activation and neutrophil degranulation are the most activated biological processes in the SARS infection as well as the neutrophilia, basophilia, and lymphopenia predicted by deconvolution analysis of samples. Thus, using Serpins and Arginase inhibitors during SARS-CoV infection may be beneficial for increasing the survival of SARS-positive patients. Regarding the high similarity of SARS-CoV-2 to SARS-CoV, the use of such inhibitors might be beneficial for COVID-19 patients
Clear-air lidar dark band
Abstract. This paper illustrates measurements carried out by the
Raman lidar BASIL in the frame of the HD(CP)2 Observational Prototype
Experiment (HOPE), revealing the presence of a clear-air dark band phenomenon
(i.e. a minimum in lidar backscatter echoes) in the upper portion of the
convective boundary layer. The phenomenon is clearly distinguishable in the
lidar backscatter echoes at 532 and 1064 nm, as well as in the particle
depolarisation data. This phenomenon is attributed to the presence of lignite
aerosol particles advected from the surrounding open pit mines in the
vicinity of the measuring site. The paper provides evidence of the phenomenon
and illustrates possible interpretations for its occurrence
Anxiety-like behavior of prenatally stressed rats is associated with a selective reduction of glutamate release in the ventral hippocampus
Abnormalities of synaptic transmission and plasticity in the hippocampus represent an integral part of the altered programming triggered by early life stress. Prenatally restraint stressed (PRS) rats develop long-lasting biochemical and behavioral changes, which are the expression of an anxious/depressive-like phenotype. We report here that PRS rats showed a selective impairment of depolarization- or kainate-stimulated glutamate and 3HD-aspartate release in the ventral hippo campus, a region encoding memories related to stress and emotions. GABA release was un affected in PRS rats. As a consequence of reduced glutamate release, PRS rats were also highly resistant to kainate-induced seizures. Abnormalities of glutamate release were associated with large reductions in the levels of synaptic vesicle-related proteins, such as VAMP (synaptobrevin), syntaxin-1, synaptophysin, synapsin Ia/b and IIa, munc-18, and Rab3A in the ventral hippocampus of PRS rats. Anxiety-like behavior in male PRS (and control) rats was inversely related to the extent of depolarization-evoked glutamate release in the ventral hippocampus. A causal relationship between anxiety-like behavior and reduction in glutamate release was demonstrated usingamixtureofthemGlu2/3 receptor antagonist, LY341495, and the GABAB receptor antagonist, CGP52432, which was shown to amplify depolarization-evoked 3HD-aspartate release in the ventral hippocampus. Bilateral micro infusion of CGP52432 plus LY341495 in the ventral hippocampus abolished anxiety-like behavior in PRS rats. These findings indicate that an impairment of glutamate release in the ventral hippocampus is a key component of the neuro plastic program induced by PRS, and that strategies aimed at enhancing glutamate release in the ventral hippocampus correct the "anxious phenotype" caused by early life stress
Crucial Physical Dependencies of the Core-Collapse Supernova Mechanism
We explore with self-consistent 2D F{\sc{ornax}} simulations the dependence
of the outcome of collapse on many-body corrections to neutrino-nucleon cross
sections, the nucleon-nucleon bremsstrahlung rate, electron capture on heavy
nuclei, pre-collapse seed perturbations, and inelastic neutrino-electron and
neutrino-nucleon scattering. Importantly, proximity to criticality amplifies
the role of even small changes in the neutrino-matter couplings, and such
changes can together add to produce outsized effects. When close to the
critical condition the cumulative result of a few small effects (including
seeds) that individually have only modest consequence can convert an anemic
into a robust explosion, or even a dud into a blast. Such sensitivity is not
seen in one dimension and may explain the apparent heterogeneity in the
outcomes of detailed simulations performed internationally. A natural
conclusion is that the different groups collectively are closer to a realistic
understanding of the mechanism of core-collapse supernovae than might have
seemed apparent.Comment: 25 pages; 10 figure
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