2,776 research outputs found
Structural Responses of Quasi-2D Colloid Fluids to Excitations Elicited by Nonequilibrium Perturbations
We investigate the response of a dense monodisperse quasi-two-dimensional
(q2D) colloid suspension when a particle is dragged by a constant velocity
optical trap. Consistent with microrheological studies of other geometries, the
perturbation induces a leading density wave and trailing wake, and we use
Stokesian Dynamics (SD) simulations to parse direct colloid-colloid and
hydrodynamic interactions. We go on to analyze the underlying individual
particle-particle collisions in the experimental images. The displacements of
particles form chains reminiscent of stress propagation in sheared granular
materials. From these data, we can reconstruct steady-state dipolar flow
patterns that were predicted for dilute suspensions and previously observed in
granular analogs to our system. The decay of this field differs, however, from
point Stokeslet calculations, indicating that the finite size of the colloids
is important. Moreover, there is a pronounced angular dependence that
corresponds to the surrounding colloid structure, which evolves in response to
the perturbation. Put together, our results show that the response of the
complex fluid is highly anisotropic owing to the fact that the effects of the
perturbation propagate through the structured medium via chains of
colloid-colloid collisions
Probing the Soft X-ray Properties and Multi-Wavelength Variability of SN2023ixf and its Progenitor
We present a detailed analysis of nearly two decades of optical/UV and X-ray
data to study the multi-wavelength pre-explosion properties and post-explosion
X-ray properties of nearby SN2023ixf located in M101. We find no evidence of
precursor activity in the optical to UV down to a luminosity of , while X-ray observations covering nearly 18
years prior to explosion show no evidence of luminous precursor X-ray emission
down to an absorbed 0.3 - 10.0 keV X-ray luminosity of erg
s. Extensive Swift observations taken post-explosion did not detect soft
X-ray emission from SN2023ixf within the first 3.3 days after first
light, which suggests a mass-loss rate for the progenitor of
yr or a radius of
cm for the circumstellar material. Our analysis also
suggests that if the progenitor underwent a mass-loss episode, this had to
occur 0.5 - 1.5 years prior to explosion, consistent with previous
estimates. Swift detected soft X-rays from SN2023ixf days after
first light, and it rose to a peak luminosity of erg s
after 10 days and has maintained this luminosity for nearly 50 days post first
light. This peak luminosity is lower than expected, given the evidence that
SN2023ixf is interacting with dense material. However, this might be a natural
consequence of an asymmetric circumstellar medium. X-ray spectra derived from
merging all Swift observations over the first 50 days are best described by a
two-component bremsstrahlung model consisting of a heavily absorbed and hotter
component similar to that found using NuSTAR, and a less-absorbed, cooler
component. We suggest that this soft component arises from cooling of the
forward shock similar to that found in Type IIn SN2010jl.Comment: 27 pages, 13 figure
Natural Dark Matter from an Unnatural Higgs Boson and New Colored Particles at the TeV Scale
The thermal relic abundance of Dark Matter motivates the existence of new
electroweak scale particles, independent of naturalness considerations.
However, most unnatural Dark Matter models do not ensure the presence of new
particles charged under SU(3)_C, resulting in challenging LHC phenomenology.
Here, we present a class of models with scalar electroweak doublet Dark Matter
that require a host of colored particles at the TeV scale. In these models, the
Higgs boson is apparently fine-tuned, but the Dark Matter doublet is kept light
without any additional fine-tuning.Comment: 1+22 pages, 5 figures. Added references. Minor clarification
Mapping the Asymmetric Thick Disk I. A Search for Triaxiality
A significant asymmetry in the distribution of faint blue stars in the inner
Galaxy, Quadrant 1 (l = 20 to 45 degrees) compared to Quadrant 4 was first
reported by Larsen & Humphreys (1996). Parker et al (2003, 2004) greatly
expanded the survey to determine its spatial extent and shape and the
kinematics of the affected stars. This excess in the star counts was
subsequently confirmed by Juric et al. (2008) using SDSS data. Possible
explanations for the asymmetry include a merger remnant, a triaxial Thick Disk,
and a possible interaction with the bar in the Disk. In this paper we describe
our program of wide field photometry to map the asymmetry to fainter magnitudes
and therefore larger distances. To search for the signature of triaxiality, we
extended our survey to higher Galactic longitudes. We find no evidence for an
excess of faint blue stars at l > 55 degrees including the faintest magnitude
interval. The asymmetry and star count excess in Quadrant 1 is thus not due to
a triaxial Thick Disk.Comment: 36 pages, 8 figures. Accepted by Astronomical Journa
Galaxy And Mass Assembly (GAMA) : the large-scale structure of galaxies and comparison to mock universes
MA acknowledges funding from the University of St Andrews and the International Centre for Radio Astronomy Research. ASGR is supported by funding from a UWA Fellowship. PN acknowledges the support of the Royal Society through the award of a University Research Fellowship and the European Research Council, through receipt of a Starting Grant (DEGAS-259586). MJIB acknowledges the financial support of the Australian Research Council Future Fellowship 100100280. TMR acknowledges support from a European Research Council Starting Grant (DEGAS-259586).From a volume-limited sample of 45 542 galaxies and 6000 groups with z ≤ 0.213, we use an adapted minimal spanning tree algorithm to identify and classify large-scale structures within the Galaxy And Mass Assembly (GAMA) survey. Using galaxy groups, we identify 643 filaments across the three equatorial GAMA fields that span up to 200 h−1 Mpc in length, each with an average of eight groups within them. By analysing galaxies not belonging to groups, we identify a secondary population of smaller coherent structures composed entirely of galaxies, dubbed ‘tendrils’ that appear to link filaments together, or penetrate into voids, generally measuring around 10 h−1 Mpc in length and containing on average six galaxies. Finally, we are also able to identify a population of isolated void galaxies. By running this algorithm on GAMA mock galaxy catalogues, we compare the characteristics of large-scale structure between observed and mock data, finding that mock filaments reproduce observed ones extremely well. This provides a probe of higher order distribution statistics not captured by the popularly used two-point correlation function.Peer reviewe
Downregulation of 26S proteasome catalytic activity promotes epithelial-mesenchymal transition.
The epithelial-mesenchymal transition (EMT) endows carcinoma cells with phenotypic plasticity that can facilitate the formation of cancer stem cells (CSCs) and contribute to the metastatic cascade. While there is substantial support for the role of EMT in driving cancer cell dissemination, less is known about the intracellular molecular mechanisms that govern formation of CSCs via EMT. Here we show that β2 and β5 proteasome subunit activity is downregulated during EMT in immortalized human mammary epithelial cells. Moreover, selective proteasome inhibition enabled mammary epithelial cells to acquire certain morphologic and functional characteristics reminiscent of cancer stem cells, including CD44 expression, self-renewal, and tumor formation. Transcriptomic analyses suggested that proteasome-inhibited cells share gene expression signatures with cells that have undergone EMT, in part, through modulation of the TGF-β signaling pathway. These findings suggest that selective downregulation of proteasome activity in mammary epithelial cells can initiate the EMT program and acquisition of a cancer stem cell-like phenotype. As proteasome inhibitors become increasingly used in cancer treatment, our findings highlight a potential risk of these therapeutic strategies and suggest a possible mechanism by which carcinoma cells may escape from proteasome inhibitor-based therapy
Galaxy And Mass Assembly (GAMA) : stellar mass functions by Hubble type
This work was supported by the Austrian Science Foundation FWF under grant P23946. AWG was supported under the Australian Research Council's funding scheme FT110100263.We present an estimate of the galaxy stellar mass function and its division by morphological type in the local (0.025 < z < 0.06) Universe. Adopting robust morphological classifications as previously presented (Kelvin et al.) for a sample of 3727 galaxies taken from the Galaxy And Mass Assembly survey, we define a local volume and stellar mass limited sub-sample of 2711 galaxies to a lower stellar mass limit of M = 109.0 MΘ. We confirm that the galaxy stellar mass function is well described by a double-Schechter function given by Μ* = 1010.64 MΘ, α1 = 0.43, φ1* = 4.18 dex-1 Mpc-3, α2 = −1.50 and φ2* = 0.74 dex-1 Mpc-3. The constituent morphological-type stellar mass functions are well sampled above our lower stellar mass limit, excepting the faint little blue spheroid population of galaxies. We find approximately 71-4+3 per cent of the stellar mass in the local Universe is found within spheroid-dominated galaxies; ellipticals and S0-Sas. The remaining 29-3+4 per cent falls predominantly within late-type disc-dominated systems, Sab-Scds and Sd-Irrs. Adopting reasonable bulge-to-total ratios implies that approximately half the stellar mass today resides in spheroidal structures, and half in disc structures. Within this local sample, we find approximate stellar mass proportions for E : S0-Sa : Sab-Scd : Sd-Irr of 34 : 37 : 24 :5.Publisher PDFPeer reviewe
Galaxy And Mass Assembly (GAMA) : refining the local galaxy merger rate using morphological information
KRVS acknowledges the Science and Technology Facilities Council (STFC) for providing funding for this project, as well as the Government of Catalonia for a research travel grant (ref. 2010 BE-00268) to begin this project at the University of Nottingham. PN acknowledges the support of the Royal Society through the award of a University Research Fellowship and the European Research Council, through receipt of a Starting Grant (DEGAS-259586).We use the Galaxy And Mass Assembly (GAMA) survey to measure the local Universe mass-dependent merger fraction and merger rate using galaxy pairs and the CAS (concentration, asymmetry, and smoothness) structural method, which identifies highly asymmetric merger candidate galaxies. Our goals are to determine which types of mergers produce highly asymmetrical galaxies and to provide a new measurement of the local galaxy major merger rate. We examine galaxy pairs at stellar mass limits down to M* = 108 M⊙ with mass ratios of 4:1) the lower mass companion becomes highly asymmetric, whereas the larger galaxy is much less affected. The fraction of highly asymmetric paired galaxies which have a major merger companion is highest for the most massive galaxies and drops progressively with decreasing mass. We calculate that the mass-dependent major merger fraction is fairly constant at ∼1.3–2 per cent within 109.5 < M* < 1011.5 M⊙, and increases to ∼4 per cent at lower masses. When the observability time-scales are taken into consideration, the major merger rate is found to approximately triple over the mass range we consider. The total comoving volume major merger rate over the range 108.0 < M* < 1011.5 M⊙ is (1.2 ± 0.5) × 10−3 h370 Mpc−3 Gyr−1.Publisher PDFPeer reviewe
Subcutaneous ofatumumab in patients with relapsing-remitting multiple sclerosis:The MIRROR study
F2c at low x
We study the heavy-quark contributions to the proton structure function
F2(x,Q2) at next-to-leading order using compact formulas at small values of
Bjorken's x variable. The formulas provide a good agreement with the modern
HERA data for F2c(x,Q2).Comment: 8 pages, 1 figure, presented on the XIV International Conference on
Symmetry Methods in Physics (SYMPHYS-XIV), Tsakhkadzor, Armenia, August 16 -
22, 201
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