249 research outputs found
The SBF Survey of Galaxy Distances. II. Local and Large-Scale Flows
We present analysis of local large scale flows using the Surface Brightness
Fluctuation (SBF) Survey for the distances to 300 early-type galaxies. Our
models of the distribution function of mean velocity and velocity dispersion at
each point in space include a uniform thermal velocity dispersion and spherical
attractors whose position, amplitude, and radial shape are free to vary. Our
fitting procedure performs a maximum likelihood fit of the model to the
observations. We obtain a Hubble constant of Ho = 77 +/- 4 +/- 7 km/s/Mpc, but
a uniform Hubble flow is not acceptable fit to the data. Inclusion of two
attractors, one of whose fit location coincides with the Virgo cluster and the
other whose fit location is slightly beyond the Centaurus clusters nearly
explain the peculiar velocities, but the quality of the fit can be further
improved by the addition of a quadrupole correction to the Hubble flow.
Although the dipole and quadrupole may be genuine manifestations of more
distant density fluctuations, we find evidence that they are more likely due to
non-spherical attractors. We find no evidence for bulk flows which include our
entire survey volume (R < 3000 km/s); our volume is at rest with respect to the
CMB. The fits to the attractors both have isothermal radial profiles (v ~ 1/r)
over a range of overdensity between about 10 and 1, but fall off more steeply
at larger radius. The best fit value for the small scale, cosmic thermal
velocity is 180 +/- 14 km/s.Comment: 37 pages, AASTeX Latex, including 30 Postscript figures, submitted to
Astrophysical Journal, July 2, 199
Effects of tyrosine kinase inhibitors on protein kinase-independent systems
AbstractTyrosine kinase inhibitors have been widely used to probe the role of tyrosine phosphorylation in cellular signalling. These inhibitors exhibit an apparent specificity for tyrosine kinases over the serine/threonine kinases but little is known about their effects on other enzymes or biological systems. We demonstrate that genistein, erbstatin and α-cyanoeinnamamides (tyrphostins) have inhibitory effects on fatty acid synthesis, lactate transport, mitochondrial oxidative phosphorylation and aldehyde dehydrogenase. We propose, therefore, that results obtained using tyrosine kinase inhibitors should be interpreted with caution, particularly if used at concentrations sufficient to inhibit these non-protein kinase-dependent events
Neurocognitive and social-communicative function of children born very preterm at 10 years of age: Associations with microorganisms recovered from the placenta parenchyma
Discovery of a new Local Group Dwarf Galaxy Candidate in UNIONS: Bo\"otes V
We present the discovery of Bo\"otes V, a new ultra-faint dwarf galaxy
candidate. This satellite is detected as a resolved overdensity of stars during
an ongoing search for new Local Group dwarf galaxy candidates in the UNIONS
photometric dataset. It has a physical half-light radius of
26.9 pc, a -band magnitude of 4.5 0.4 mag, and
resides at a heliocentric distance of approximately 100 kpc. We use Gaia DR3
astrometry to identify member stars, characterize the systemic proper motion,
and confirm the reality of this faint stellar system. The brightest star in
this system was followed up using Gemini GMOS-N long-slit spectroscopy and is
measured to have a metallicity of [Fe/H] 2.85 0.10 dex and a
heliocentric radial velocity of = 5.1 13.4 km s. Bo\"otes V
is larger (in terms of scale radius), more distant, and more metal-poor than
the vast majority of globular clusters. It is likely that Bo\"otes V is an
ultra-faint dwarf galaxy, though future spectroscopic studies will be necessary
to definitively classify this object.Comment: 13 pages, 7 figures, 3 tables. Accepted for publication in the AAS
Journals. Please note that this paper was submitted in coordination with the
work of William Cerny et al. 2022. These authors independently discovered
this same satellite so our two research groups have coordinated the
submission of these discovery paper
The crafting of an (un)enterprising community: context and the social practice of talk
YesThis article examines a ‘deprived’ UK community to identify how (dis)connections between
context and enterprise are produced within accounts of a particular locality. We used a
discursive psychological approach to examine how the community depicted itself as a context for
enterprise. Our analysis identified three discursive repertoires mobilised by a range of voices in
the community which combined to portray an unenterprising community and create a conceptual
deadlock for enterprise. We suggest it is too deterministic to assume context is fixed and controls
the potential for entrepreneurial development. Instead, we should consider social practices,
including talk, that help construct the contexts in which entrepreneurship is expected to occur.The research resorted in this article was funded by an Economic and Social Research Council studentship
The discovery of the faintest known Milky Way satellite using UNIONS
We present the discovery of Ursa Major III/UNIONS 1, the least luminous known
satellite of the Milky Way, which is estimated to have an absolute V-band
magnitude of mag, equivalent to a total stellar mass of
16 M. Ursa Major III/UNIONS 1 was uncovered in the deep,
wide-field Ultraviolet Near Infrared Optical Northern Survey (UNIONS) and is
consistent with an old ( Gyr), metal-poor ([Fe/H] )
stellar population at a heliocentric distance of 10 kpc. Despite being
compact ( pc) and composed of so few stars, we confirm
the reality of Ursa Major III/UNIONS 1 with Keck II/DEIMOS follow-up
spectroscopy and identify 11 radial velocity members, 8 of which have full
astrometric data from and are co-moving based on their proper motions.
Based on these 11 radial velocity members, we derive an intrinsic velocity
dispersion of km s but some caveats preclude this
value from being interpreted as a direct indicator of the underlying
gravitational potential at this time. Primarily, the exclusion of the largest
velocity outlier from the member list drops the velocity dispersion to
km s, and the subsequent removal of an additional
outlier star produces an unresolved velocity dispersion. While the presence of
binary stars may be inflating the measurement, the possibility of a significant
velocity dispersion makes Ursa Major III/UNIONS 1 a high priority candidate for
multi-epoch spectroscopic follow-ups to deduce to true nature of this
incredibly faint satellite.Comment: 21 pages, 9 figures, 3 tables; Accepted for publication in Ap
Pacific Atmospheric Sulfur Experiment (PASE): dynamics and chemistry of the south Pacific tropical trade wind regime
The Pacific Atmospheric Sulfur Experiment (PASE) was a comprehensive airborne study of the chemistry and dynamics of the tropical trade wind regime (TWR) east of the island of Kiritibati (Christmas Island, 157º, 20′ W, 2º 52′ N). Christmas Island is located due south of Hawaii. Geographically it is in the northern hemisphere yet it is 6–12º south of the intertropical convergence zone (ITCZ) which places it in the southern hemisphere meteorologically. Christmas Island trade winds in August and September are from east south east at 3–15 ms−1. Clouds, if present, are fair weather cumulus located in the middle layer of the TWR which is frequently labeled the buffer layer (BuL). PASE provided clear support for the idea that small particles (80 nm) were subsiding into the tropical trade wind regime (TWR) where sulfur chemistry transformed them to larger particles. Sulfur chemistry promoted the growth of some of these particles until they were large enough to activate to cloud drops. This process, promoted by sulfur chemistry, can produce a cooling effect due to the increase in cloud droplet density and changes in cloud droplet size. These increases in particle size observed in PASE promote additional cooling due to direct scattering from the aerosol. These potential impacts on the radiation balance in the TWR are enhanced by the high solar irradiance and ocean albedo of the TWR. Finally because of the large area involved there is a large factional impact on earth’s radiation budget. The TWR region near Christmas Island appears to be similar to the TWR that persists in August and September, from southwest of the Galapagos to at least Christmas Island. Transport in the TWR between the Galapagos and Christmas involves very little precipitation which could have removed the aerosol thus explaining at least in part the high concentrations of CCN (≈300 at 0.5% supersaturation) observed in PASE. As expected the chemistry of sulfur in the trade winds was found to be initiated by the emission of DMS into the convective boundary layer (BL, the lowest of three layers). However, the efficiency with which this DMS is converted to SO2 has been brought into further question by this study. This unusual result has come about as result of our using two totally different approaches for addressing this long standing question. In the first approach, based on accepted kinetic rate constants and detailed steps for the oxidation of DMS reflecting detailed laboratory studies, a DMS to SO2 conversion efficiency of 60–73% was determined. This range of values lies well within the uncertainties of previous studies. However, using a completely different approach, involving a budget analysis, a conversion value of 100% was estimated. The latter value, to be consistent with all other sulfur studies, requires the existence of a completely independent sulfur source which would emit into the atmosphere at a source strength approximately half that measured for DMS under tropical Pacific conditions. At this time, however, there is no credible scientific observation that identifies what this source might be. Thus, the current study has opened for future scientific investigation the major question: is there yet another major tropical marine source of sulfur? Of equal importance, then, is the related question, is our global sulfur budget significantly in error due to the existence of an unknown marine source of sulfur? Pivotal to both questions may be gaining greater insight about the intermediate DMS oxidation species, DMSO, for which rather unusual measurements have been reported in previous marine sulfur studies. The 3 pptv bromine deficit observed in PASE must be lost over the lifetime of the aerosol which is a few days. This observation suggests that the primary BrO production rate is very small. However, considering the uncertainties in these observations and the possible importance of secondary production of bromine radicals through aerosol surface reactions, to completely rule out the importance of bromine chemistry under tropical conditions at this time cannot be justified. This point has been brought into focus from prior work that even at levels of 1 pptv, the effect of BrO oxidation on DMS can still be quite significant. Thus, as in the case of DMS conversion to SO2, future studies will be needed. In the latter case there will need to be a specific focus on halogen chemistry. Such studies clearly must involve specific measurements of radical species such as BrO
Cross Sections of the 83Rb (p,γ)84Sr and 84Kr(p,γ)85Rb Reactions at Energies Characteristic of the Astrophysical γ Process
We have measured the cross section of the 83 Rb ( p , γ ) 84 Sr radiative capture reaction in inverse kinematics using a radioactive beam of 83 Rb at incident energies of 2.4 and 2.7 A MeV. Prior to the radioactive beam measurement, the 84 Kr ( p , γ ) 85 Rb radiative capture reaction was measured in inverse kinematics using a stable beam of 84 Kr at an incident energy of 2.7 A MeV. The effective relative kinetic energies of these measurements lie within the relevant energy window for the γ process in supernovae. The central values of the measured partial cross sections of both reactions were found to be 0.17 – 0.42 times the predictions of statistical model calculations. Assuming the predicted cross section at other energies is reduced by the same factor leads to a slightly higher calculated abundance of the p nucleus 84 Sr , caused by the reduced rate of the 84 Sr ( γ , p ) 83 Rb reaction derived from the present measurement
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