300 research outputs found
Periodicities in an active region correlated with Type III radio bursts observed by Parker Solar Probe
Context. Periodicities have frequently been reported across many wavelengths
in the solar corona. Correlated periods of ~5 minutes, comparable to solar
p-modes, are suggestive of coupling between the photosphere and the corona.
Aims. Our study investigates whether there are correlations in the periodic
behavior of Type III radio bursts, indicative of non-thermal electron
acceleration processes, and coronal EUV emission, assessing heating and
cooling, in an active region when there are no large flares. Methods. We use
coordinated observations of Type III radio bursts from the FIELDS instrument on
Parker Solar Probe (PSP), of extreme ultraviolet emissions by the Solar
Dynamics Observatory (SDO)/AIA and white light observations by SDO/HMI, and of
solar flare x-rays by Nuclear Spectroscopic Telescope Array (NuSTAR) on April
12, 2019. Several methods for assessing periodicities are utilized and compared
to validate periods obtained. Results. Periodicities of about 5 minutes in the
EUV in several areas of an active region are well correlated with the
repetition rate of the Type III radio bursts observed on both PSP and Wind.
Detrended 211A and 171A light curves show periodic profiles in multiple
locations, with 171A peaks lagging those seen in 211A. This is suggestive of
impulsive events that result in heating and then cooling in the lower corona.
NuSTAR x-rays provide evidence for at least one microflare during the interval
of Type III bursts, but there is not a one-to-one correspondence between the
x-rays and the Type-III bursts. Our study provides evidence for periodic
acceleration of non-thermal electrons (required to generate Type III radio
bursts) when there were no observable flares either in the x-ray data or the
EUV. The acceleration process, therefore, must be associated with small
impulsive events, perhaps nanoflares
Novel Mouse Model for Analysis of Macrophage Function in Neuroblastoma
Background: Neuroblastoma is the third most common childhood cancer and accounts for 12% of cancer-associated deaths in children under the age of 15. Patients with high risk neuroblastoma have a poor 5-year survival rate of less than 50%. Neuroblastoma tumors treated with the histone deacetylase inhibitor (HDACi) vorinostat have increased infiltration of macrophages with upregulated immune cell-surface receptors. Neuroblastoma cells release VEGF and M-CSF, which may alter intratumoral macrophage populations. VEGF has also been implicated in alteration of amyloid precursor protein family processing. Our lab demonstrated that amyloid precursor protein 2 (APLP2), a member of the amyloid precursor protein family, plays an important role in the migration of tumor cells. APLP2 is known to be expressed by macrophages, but no studies have previously examined macrophage functions that are impacted by APLP2 in the context of neuroblastoma disease and its treatment by HDACi drugs.
Significance of Problem: Because of the high morbidity and mortality associated with neuroblastoma, studies such as this one that are designed to comprehend the interaction of immunity and treatment in neuroblastoma are clinically significant. The results from this study are also expected to expand our comprehension of macrophage function and regulation, and thus will be of broad value in the immunology and oncology fields.
Experimental Design and Results: We have treated neuroblastoma tumor cells in vitro with M344, an HDACi with structural similarity to vorinostat, and showed that M344 decreases neuroblastoma cell growth. In addition, we have generated mice that lack APLP2 expression in cells expressing the Csf-1 receptor (a protein characteristically expressed by macrophages and dendritic cells). We discovered that following polarization, macrophages collected from the bone marrow of these mice have an altered distribution of M1 and M2 sub-populations, which are macrophage sub-populations known to differ in their migratory capabilities. Furthermore, we have shown that M1 and M2 subpopulations of bone marrow-derived macrophages from normal mice differ in their expression of APLP2. Thus, APLP2 is influential in macrophage biology, and we have created a novel mouse model for defining its specific contributions in mice treated with HDACi that influence macrophage biology.
Conclusions: Based on the data that we have acquired, we are well positioned to fully explore both the impact of HDACi drugs on macrophage/dendritic cell populations in a syngeneic neuroblastoma mouse model, and to define the role of APLP2 in the function of these cell populations in the context of neuroblastoma.https://digitalcommons.unmc.edu/chri_forum/1000/thumbnail.jp
Chemotherapy-induced senescent cancer cells engulf other cells to enhance their survival.
In chemotherapy-treated breast cancer, wild-type p53 preferentially induces senescence over apoptosis, resulting in a persisting cell population constituting residual disease that drives relapse and poor patient survival via the senescence-associated secretory phenotype. Understanding the properties of tumor cells that allow survival after chemotherapy treatment is paramount. Using time-lapse and confocal microscopy to observe interactions of cells in treated tumors, we show here that chemotherapy-induced senescent cells frequently engulf both neighboring senescent or nonsenescent tumor cells at a remarkable frequency. Engulfed cells are processed through the lysosome and broken down, and cells that have engulfed others obtain a survival advantage. Gene expression analysis showed a marked up-regulation of conserved macrophage-like program of engulfment in chemotherapy-induced senescent cell lines and tumors. Our data suggest compelling explanations for how senescent cells persist in dormancy, how they manage the metabolically expensive process of cytokine production that drives relapse in those tumors that respond the worst, and a function for their expanded lysosomal compartment
A Role for the Juxtamembrane Cytoplasm in the Molecular Dynamics of Focal Adhesions
Focal adhesions (FAs) are specialized membrane-associated multi-protein complexes that link the cell to the extracellular matrix and play crucial roles in cell-matrix sensing. Considerable information is available on the complex molecular composition of these sites, yet the regulation of FA dynamics is largely unknown. Based on a combination of FRAP studies in live cells, with in silico simulations and mathematical modeling, we show that the FA plaque proteins paxillin and vinculin exist in four dynamic states: an immobile FA-bound fraction, an FA-associated fraction undergoing exchange, a juxtamembrane fraction experiencing attenuated diffusion, and a fast-diffusing cytoplasmic pool. The juxtamembrane region surrounding FAs displays a gradient of FA plaque proteins with respect to both concentration and dynamics. Based on these findings, we propose a new model for the regulation of FA dynamics in which this juxtamembrane domain acts as an intermediary layer, enabling an efficient regulation of FA formation and reorganization
Constraints on the cosmic expansion history from GWTC-3
We use 47 gravitational-wave sources from the Third LIGO-Virgo-KAGRA Gravitational-Wave Transient Catalog (GWTC-3) to estimate the Hubble parameter , including its current value, the Hubble constant . Each gravitational-wave (GW) signal provides the luminosity distance to the source and we estimate the corresponding redshift using two methods: the redshifted masses and a galaxy catalog. Using the binary black hole (BBH) redshifted masses, we simultaneously infer the source mass distribution and . The source mass distribution displays a peak around , followed by a drop-off. Assuming this mass scale does not evolve with redshift results in a measurement, yielding ( credible interval) when combined with the measurement from GW170817 and its electromagnetic counterpart. This represents an improvement of 17% with respect to the estimate from GWTC-1. The second method associates each GW event with its probable host galaxy in the catalog GLADE+, statistically marginalizing over the redshifts of each event's potential hosts. Assuming a fixed BBH population, we estimate a value of with the galaxy catalog method, an improvement of 42% with respect to our GWTC-1 result and 20% with respect to recent studies using GWTC-2 events. However, we show that this result is strongly impacted by assumptions about the BBH source mass distribution; the only event which is not strongly impacted by such assumptions (and is thus informative about ) is the well-localized event GW190814
Search for gravitational waves from Scorpius X-1 with a hidden Markov model in O3 LIGO data
Results are presented for a semi-coherent search for continuous gravitational waves from the low-mass X-ray binary Scorpius X-1, using a hidden Markov model (HMM) to allow for spin wandering. This search improves on previous HMM-based searches of Laser Interferometer Gravitational-wave Observatory (LIGO) data by including the orbital period in the search template grid, and by analyzing data from the latest (third) observing run (O3). In the frequency range searched, from 60 to 500 Hz, we find no evidence of gravitational radiation. This is the most sensitive search for Scorpius X-1 using a HMM to date. For the most sensitive sub-band, starting at Hz, we report an upper limit on gravitational wave strain (at confidence) of , assuming the orbital inclination angle takes its electromagnetically restricted value . The upper limits on gravitational wave strain reported here are on average a factor of lower than in the O2 HMM search. This is the first Scorpius X-1 HMM search with upper limits that reach below the indirect torque-balance limit for certain sub-bands, assuming
First joint observation by the underground gravitational-wave detector KAGRA with GEO 600
We report the results of the first joint observation of the KAGRA detector with GEO 600. KAGRA is a cryogenic and underground gravitational-wave detector consisting of a laser interferometer with 3 km arms, located in Kamioka, Gifu, Japan. GEO 600 is a British-German laser interferometer with 600 m arms, located near Hannover, Germany. GEO 600 and KAGRA performed a joint observing run from April 7 to 20, 2020. We present the results of the joint analysis of the GEO-KAGRA data for transient gravitational-wave signals, including the coalescence of neutron-star binaries and generic unmodeled transients. We also perform dedicated searches for binary coalescence signals and generic transients associated with gamma-ray burst events observed during the joint run. No gravitational-wave events were identified. We evaluate the minimum detectable amplitude for various types of transient signals and the spacetime volume for which the network is sensitive to binary neutron-star coalescences. We also place lower limits on the distances to the gamma-ray bursts analyzed based on the non-detection of an associated gravitational-wave signal for several signal models, including binary coalescences. These analyses demonstrate the feasibility and utility of KAGRA as a member of the global gravitational-wave detector network
Search for anisotropic gravitational-wave backgrounds using data from Advanced LIGO and Advanced Virgo's first three observing runs
We report results from searches for anisotropic stochastic gravitational-wave
backgrounds using data from the first three observing runs of the Advanced LIGO
and Advanced Virgo detectors. For the first time, we include Virgo data in our
analysis and run our search with a new efficient pipeline called {\tt PyStoch}
on data folded over one sidereal day. We use gravitational-wave radiometry
(broadband and narrow band) to produce sky maps of stochastic
gravitational-wave backgrounds and to search for gravitational waves from point
sources. A spherical harmonic decomposition method is employed to look for
gravitational-wave emission from spatially-extended sources. Neither technique
found evidence of gravitational-wave signals. Hence we derive 95\%
confidence-level upper limit sky maps on the gravitational-wave energy flux
from broadband point sources, ranging from and on the
(normalized) gravitational-wave energy density spectrum from extended sources,
ranging from , depending on direction () and spectral index
(). These limits improve upon previous limits by factors of . We also set 95\% confidence level upper limits on the frequency-dependent
strain amplitudes of quasimonochromatic gravitational waves coming from three
interesting targets, Scorpius X-1, SN 1987A and the Galactic Center, with best
upper limits range from a factor of
improvement compared to previous stochastic radiometer searches.Comment: 23 Pages, 9 Figure
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