1,165 research outputs found
Factors determining exchange rates : a simple model and empirical tests
An abstract for this article is not availableEquilibrium (Economics)
Differential Effects of Viewpoint on Object-Driven Activation in Dorsal and Ventral Streams
AbstractUsing fMRI, we showed that an area in the ventral temporo-occipital cortex (area vTO), which is part of the human homolog of the ventral stream of visual processing, exhibited priming for both identical and depth-rotated images of objects. This pattern of activation in area vTO corresponded to performance in a behavioral matching task. An area in the caudal part of the intraparietal sulcus (area cIPS) also showed priming, but only with identical images of objects. This dorsal-stream area treated rotated images as new objects. The difference in the pattern of priming-related activation in the two areas may reflect the respective roles of the ventral and dorsal streams in object recognition and object-directed action
The slope of the mass profile and the tilt of the fundamental plane in early-type galaxies
We present a survey, using the Chandra X-ray observatory, of the central
gravitating mass profiles in a sample of 10 galaxies, groups and clusters,
spanning ~2 orders of magnitude in virial mass. We find the total mass
distributions from ~0.2--10Re, where Re is the optical effective radius of the
central galaxy, are remarkably similar to powerlaw density profiles. The
negative logarithmic slope of the mass density profiles, alpha, systematically
varies with Re, from alpha=2, for systems with Re~4kpc to alpha=1.2 for systems
with Re>30kpc. Departures from hydrostatic equilibrium are likely to be small
and cannot easily explain this trend. We show that the conspiracy between the
baryonic (Sersic) and dark matter (NFW/ Einasto) components required to
maintain a powerlaw total mass distribution naturally predicts an
anti-correlation between alpha and Re that is very close to what is observed.
The systematic variation of alpha with Re implies a dark matter fraction within
Re that varies systematically with the properties of the galaxy in such a
manner as to reproduce, without fine tuning, the observed tilt of the
fundamental plane. We speculate that establishing a nearly powerlaw total mass
distribution is therefore a fundamental feature of galaxy formation and the
primary factor which determines the tilt of the fundamental plane.Comment: 10 pages, 5 figures, 2 tables. Accepted for publication in MNRAS.
Minor revisions to match accepted versio
Non perturbative chiral approach to s-wave \bar{K}N interactions
The s-wave meson-nucleon interaction in the sector is studied by
means of coupled-channel Lippmann Schwinger equations, using the lowest order
chiral Lagrangian and a cut off to regularize the loop integrals. The method
reproduces succesfully the resonance and the cross
sections at low energies. The inclusion of the
channels in the coupled system is found very important and allows a solution in
terms of only the lowest order Lagrangian.Comment: 34 pages, 11 figures, uses epsf.sty, submitted to Nucl.Phys.
Dark matter halos around isolated ellipticals
We investigate the distribution of the luminous and the dark matter
components in the isolated ellipticals NGC 7052 and NGC 7785, embedded in an
emitting hot gas halo, by means of relevant X-ray and photometric data. In
order to calculate the dark matter distribution in these rare objects, we
performed an improved X-ray analysis of the XMM-Newton data of NGC 7785, and we
used former results based on Chandra data of NGC 7052. For each object we also
derived the stellar spheroid length scale from the surface photometry and the
spheroid stellar mass from an analysis of the galaxy spectral energy
distribution. We find that a dark matter component is present in these objects.
It is subdominant and mixed with the luminous matter inside the optical region
half-light radius wide, while it dominates the gravitational potential at outer
radii. On the whole, the dark halo structure is very similar to that found
around spirals of comparable luminosity and it is well reproduced by a Burkert
halo, while a Sersic spheroid accounts well for the baryonic component.Comment: 9 pages, 5 figures, matching the version published by Astronomy &
Astrophysic
Pharmacokinetics and pharmacodynamics of a human monoclonal anti‐FGF23 antibody (KRN23) in the first multiple ascending‐dose trial treating adults with X‐linked hypophosphatemia
In X-linked hypophosphatemia (XLH), serum fibroblast growth factor 23 (FGF23) is increased and results in reduced renal maximum threshold for phosphate reabsorption (TmP), reduced serum inorganic phosphorus (Pi), and inappropriately low normal serum 1,25 dihydroxyvitamin D (1,25[OH]2D) concentration, with subsequent development of rickets or osteomalacia. KRN23 is a recombinant human IgG1 monoclonal antibody that binds to FGF23 and blocks its activity. Up to 4 doses of KRN23 were administered subcutaneously every 28 days to 28 adults with XLH. Mean ± standard deviation KRN23 doses administered were 0.05, 0.10 ± 0.01, 0.28 ± 0.06, and 0.48 ± 0.16 mg/kg. The mean time to reach maximum serum KRN23 levels was 7.0 to 8.5 days. The mean KRN23 half-life was 16.4 days. The mean area under the concentration–time curve (AUCn) for each dosing interval increased proportionally with increases in KRN23 dose. The mean intersubject variability in AUCn ranged from 30% to 37%. The area under the effect concentration–time curve (AUECn) for change from baseline in TmP per glomerular filtration rate, serum Pi, 1,25(OH)2D, and bone markers for each dosing interval increased linearly with increases in KRN23 AUCn. Linear correlation between serum KRN23 concentrations and increase in serum Pi support KRN23 dose adjustments based on predose serum Pi concentration
Temporal changes in distributions and the species atlas: how can British and Irish plant data shoulder the inferential burden?
Species distribution atlases often rely on volunteer effort to achieve their desired coverage, an activity now typically discussed, at least in academia, under the general theme of “citizen science”. Such data, however, are rarely without complex biases, particularly with respect to the estimation of trends in species’ distributions over many decades. The data of the Botanical Society of Britain and Ireland (BSBI) are no exception to this, and both careful thought in data aggregation (spatial, temporal, and taxonomic) and appropriate modelling procedures are required to overcome these challenges. We discuss these issues, with a primary focus on the statistical models that have been put forward to adjust for such biases. Such models include the Telfer method, various “reporting rate” approaches based on generalised linear models, the frequency scaling using local occupancy (“Frescalo”) model, occupancy models, and spatial smoothing methods. In each case the strengths and limitations in relation to estimating trends from distribution data with important time-varying biases are assessed. Various properties of BSBI data, in particular the increasing numbers of records at fine spatial and temporal scales over the past century, coupled with a general lack of re-visits to sites at such finer scales and the time-varying biases previously mentioned, imply that methods that can be sensibly applied at coarser levels are likely to be most appropriate for estimating accurate long-term trends in distributions. We conclude that Frescalo, which can be seen as a type of occupancy model where an adjustment for overlooked species is made in relation to spatial rather than temporal replication, whilst simultaneously adjusting for variable regional effort, is currently the most sophisticated tool for achieving this. Although recording community-accepted adjustments to data collection practices may allow for a greater application of occupancy modelling or other approaches in the future, methods that seek accurate trends over the long-term are necessarily limited either to scales at which various properties of the data in hand are most likely to be unbiased, or at which the biases are well enough understood to be modelled accurately
Salmonella typhimurium's transthyretin-like protein is a host-specific factor important in fecal survival in chickens.
The transthyretin-like protein (TLP) from Salmonella enterica subspecies I is a periplasmic protein with high level structural similarity to a protein found in mammals and fish. In humans, the protein homologue, transthyretin, binds and carries retinol and thyroxine, and a series of other, unrelated aromatic compounds. Here we show that the amino acid sequence of the TLP from different species, subspecies and serovars of the Salmonella genus is highly conserved and demonstrate that the TLP gene is constitutively expressed in S. Typhimurium and that copper and other divalent metal ions severely inhibit enzyme activity of the TLP, a cyclic amidohydrolase that hydrolyses 5-hydroxyisourate (5-HIU). In order to determine the in vivo role of the S. Typhimurium TLP, we constructed a strain of mouse-virulent S. Typhimurium SL1344 bearing a mutation in the TLP gene (SL1344 ΔyedX). We assessed the virulence of this strain via oral inoculation of mice and chickens. Whilst SL1344 ΔyedX induced a systemic infection in both organisms, the bacterial load detected in the faeces of infected chickens was significantly reduced when compared to the load of S. Typhimurium SL1344. These data demonstrate that the TLP gene is required for survival of S. Typhimurium in a high uric acid environment such as chicken faeces, and that metabolic traits of Salmonellae in natural and contrived hosts may be fundamentally different. Our data also highlight the importance of using appropriate animal models for the study of bacterial pathogenesis especially where host-specific virulence factors or traits are the subject of the study
Abundance ratios in the hot ISM of elliptical galaxies
To constrain the recipes put forth to solve the theoretical Fe discrepancy in
the hot interstellar medium of elliptical galaxies and at the same time explain
the [alpha/Fe] ratios. In order to do so we use the latest theoretical
nucleosynthetic yields, we incorporate the dust, we explore differing SNIa
progenitor scenarios by means of a self-consistent chemical evolution model
which reproduces the properties of the stellar populations in elliptical
galaxies. Models with Fe-only dust and/or a lower effective SNIa rate achieve a
better agreement with the observed Fe abundance. However, a suitable
modification to the SNIa yield with respect to the standard W7 model is needed
to fully match the abundance ratio pattern. The 2D explosion model C-DDT by
Maeda et al. (2010) is a promising candidate for reproducing the [Fe/H] and the
[alpha/Fe] ratios. (A&A format)Comment: 11 pages, 4 figures, to appear on A&
DTMp : a comenius 2.1 project to produce a differentiated teaching module for primary school trainee teachers
This work was supported by the EU through Comenius 2.1 granr no. 118096 for the DTMp Project.As European classrooms become more heterogeneous, the movement towards inclusive education becomes more urgent as well as more challenging. This paper describes the process of developing and running a proposal for a Comenius 2.1 project aimed at developing training materials for the preparation of pre-service teachers in responding to diversity in primary classrooms. The project, started in October 2004, has collected the concerns and experiences of responding to diversity of 35 teachers (5 each from 7 different countries) through semi-structured interviews, and produced the first draft of a multilingual handbook for trainees. The handbook in hard copy and web-based format, will be piloted in 2005-06 in the seven participating countries, namely Malta (coordinator), Czech Republic, Germany, Lithuania, Netherlands, Sweden and the UK. This paper will focus on the process of trans-European sharing of research and development of the training course.peer-reviewe
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