4,849 research outputs found
The baryonic Tully-Fisher relation for different velocity definitions and implications for galaxy angular momentum
We study the baryonic Tully-Fisher relation (BTFR) at z=0 using 153 galaxies
from the SPARC sample. We consider different definitions of the characteristic
velocity from HI and H-alpha rotation curves, as well as HI line-widths from
single-dish observations. We reach the following results: (1) The tightest BTFR
is given by the mean velocity along the flat part of the rotation curve. The
orthogonal intrinsic scatter is extremely small (6%) and the best-fit slope is
3.85+/-0.09, but systematic uncertainties may drive the slope from 3.5 to 4.0.
Other velocity definitions lead to BTFRs with systematically higher scatters
and shallower slopes. (2) We provide statistical relations to infer the flat
rotation velocity from HI line-widths or less extended rotation curves (like
H-alpha and CO data). These can be useful to study the BTFR from large HI
surveys or the BTFR at high redshifts. (3) The BTFR is more fundamental than
the relation between angular momentum and galaxy mass (the Fall relation). The
Fall relation has about 7 times more scatter than the BTFR, which is merely
driven by the scatter in the mass-size relation of galaxies. The BTFR is
already the "fundamental plane" of galaxy discs: no value is added with a
radial variable as a third parameter.Comment: 12 pages, 6 figures, accepted for publication in MNRA
From academic communities to managed organisations: the implications for academic careers in UK and German universities
This paper examines the implications for academic careers of the apparent global trend towards marketisation and managerialism in higher education with reference to the UK
and Germany. It discusses how university employers might exercise greater control over their employees, privileging research and international publication, and fragmenting the traditional unity of the academic role. The effect is to challenge the values of academic communities, subject
individuals to greater uncertainty, competition and insecurity, and influence the shape and direction of academic careers. The paper notes how todays academic careers could be understood in terms of Kanters three forms of career as well as the boundaryless and protean career. However, it argues that these approaches do not address the key issue in both the UK and German cases: the changed locus and exercise of power within the employment relationship. It concludes that, to understand how careers are changing, this power relationship and the context of career in general have to be taken into account
Prevalence of clinical autistic traits within a homeless population: barriers to accessing homeless services
Recent research suggests a high prevalence rate of Autism Spectrum Conditions (ASC) amongst the homeless population. Although, it is well-documented that autistic people experienced many barriers to accessing health services, little is known about their challenges in accessing homeless services. Thus, the present study aimed to measure prevalence of high levels of autistic traits, and to identify barriers that prevent autistic people accessing homeless services. Participants recruited from homeless services (n = 65) completed the Autism Quotient-10 (AQ-10) alongside a questionnaire regarding perceived accessibility of homeless services. Results revealed that 18.5% of participants scored Above the Clinical Threshold of the AQ-10 (ACT-AQ). Moreover, the ACT-AQ group reported that encountering big groups in shared accommodation represent a significant barrier to engaging with homeless services. Further research is needed to identify the full degree of ASC representation and the factors that might prevent autistic homeless people accessing homeless services, and thus overcoming homelessness
Testing Feedback-Modified Dark Matter Haloes with Galaxy Rotation Curves: Estimation of Halo Parameters and Consistency with CDM
Cosmological -body simulations predict dark matter (DM) haloes with steep
central cusps (e.g. NFW, Navarro et al. 1996). This contradicts observations of
gas kinematics in low-mass galaxies that imply the existence of shallow DM
cores. Baryonic processes such as adiabatic contraction and gas outflows can,
in principle, alter the initial DM density profile, yet their relative
contributions to the halo transformation remain uncertain. Recent high
resolution, cosmological hydrodynamic simulations (Di Cintio et al. 2014, DC14)
predict that inner density profiles depend systematically on the ratio of
stellar to DM mass (M/M). Using a Markov Chain Monte Carlo
approach, we test the NFW and the M/M-dependent DC14 halo
models against a sample of 147 galaxy rotation curves from the new {\it
Spitzer} Photometry and Accurate Rotation Curves (SPARC) data set. These
galaxies all have extended H{\small I} rotation curves from radio
interferometry as well as accurate stellar mass density profiles from
near-infrared photometry. The DC14 halo profile provides markedly better fits
to the data compared to the NFW profile. Unlike NFW, the DC14 halo parameters
found in our rotation curve fits naturally fall within two standard deviations
of the mass-concentration relation predicted by CDM and the stellar
mass-halo mass relation inferred from abundance matching with few outliers.
Halo profiles modified by baryonic processes are therefore more consistent with
expectations from cold dark matter (CDM) cosmology and
provide better fits to galaxy rotation curves across a wide range of galaxy
properties than do halo models that neglect baryonic physics. Our results offer
a solution to the decade long cusp-core discrepancy.Comment: 23 Pages, 18 Figures, MNRAS Accepte
Coral Disease and Health Workshop: Coral Histopathology II
The health and continued existence of coral reef ecosystems are threatened by an increasing array of environmental and anthropogenic impacts. Coral disease is one of the prominent causes of increased mortality among reefs globally, particularly in the Caribbean. Although over 40 different coral diseases and syndromes have been reported
worldwide, only a few etiological agents have been confirmed; most pathogens remain unknown and the dynamics of disease transmission, pathogenicity and mortality are not
understood. Causal relationships have been documented for only a few of the coral diseases, while new syndromes continue to emerge. Extensive field observations by coral
biologists have provided substantial documentation of a plethora of new pathologies, but our understanding, however, has been limited to descriptions of gross lesions with names reflecting these observations (e.g., black band, white band, dark spot). To determine etiology, we must equip coral diseases scientists with basic biomedical knowledge and specialized training in areas such as histology, cell biology and pathology. Only through
combining descriptive science with mechanistic science and employing the synthesis epizootiology provides will we be able to gain insight into causation and become equipped to handle the pending crisis.
One of the critical challenges faced by coral disease researchers is to establish a framework to systematically study coral pathologies drawing from the field of diagnostic
medicine and pathology and using generally accepted nomenclature. This process began in April 2004, with a workshop titled Coral Disease and Health Workshop: Developing Diagnostic Criteria co-convened by the Coral Disease and Health Consortium (CDHC), a working group organized under the auspices of the U.S. Coral Reef Task Force, and the International Registry for Coral Pathology (IRCP). The workshop was hosted by the U.S. Geological Survey, National Wildlife Health Center (NWHC) in Madison, Wisconsin and was focused on gross morphology and disease signs observed in the field. A resounding recommendation from the histopathologists participating in the workshop was the urgent need to develop diagnostic criteria that are suitable to move from gross observations to morphological diagnoses based on evaluation of microscopic anatomy. (PDF contains 92 pages
Loudly sing cuckoo : More-than-human seasonalities in Britain
This research was funded by a grant from the Arts and Humanities Research Council, grant number AH/E009573/1.Peer reviewedPostprin
Spin-orbit fields in asymmetric (001)-oriented GaAs/AlxGa 1-xAs quantum wells
We measure simultaneously the in-plane electron g factor and spin-relaxation rate in a series of undoped inversion-asymmetric (001)-oriented GaAs/AlGaAs quantum wells by spin-quantum beat spectroscopy. In combination the two quantities reveal the absolute values of both the Rashba and the Dresselhaus coefficients and prove that the Rashba coefficient can be negligibly small despite huge conduction-band potential gradients which break the inversion symmetry. The negligible Rashba coefficient is a consequence of the "isomorphism" of conduction- and valence-band potentials in quantum systems where the asymmetry is solely produced by alloy variations. © 2011 American Physical Society
- …