38 research outputs found
Migration and divisions:thoughts on (anti-) narrativity in visual representations of mobile people
This article developed as part of a dialogue between the two authors. The dialogue was sparked off by MARLEY's response to a seminar presentation by GILLIGAN. In keeping with its origins we have retained the dialogue format. The article focuses on two sets of images—one a still image taken by a photojournalist, the other a sequence of stills taken by one of the authors. The authors use these images to explore the question "what imbues an image with narrative content?" and to explore the possibilities for developing a positive visual representation which promotes the idea of open borders. The article draws on linguistic theory to explore the grammar of visual narrative and relates this to the issue of the visual representation of immigration in contemporary Europe
Second order predictor-corrector pairs
The purpose of this study is to introduce multistep methods for approximating the solutions of ordinary differential equations and to study the general convergent, second order, predictor-corrector pair. Given the values of a solution function, either exact or approximate, at certain points on the x-axis, a multistep method approximates the values of that function at other points on the x-axis. Necessary and sufficient conditions for the convergence of a multistep method are the conditions of consistency and stability. A multistep method which approximates the value of the solution function y at xN with no knowledge of the value of the derivative y1 at xN is called a predictor. A corrector is a multistep method which uses the value of the derivative of y at xN to approximate y at xN. The predictor is used to generate a rough estimate of the solution function at a point x then the corrector is used to correct the predicted value at xN . Used together they constitute a predictor-corrector pair. If the differential equation to be solved is of the form y' = ?y, the predictor can be substituted in the corrector to yield a linear recursion. Constraints on the roots of the recursion which would ensure convergence to the true solution are discussed along with their applicability to equations of the form y' = f(x,y)
The JWST Early Release Science Program for Direct Observations of Exoplanetary Systems II: A 1 to 20 Micron Spectrum of the Planetary-Mass Companion VHS 1256-1257 b
We present the highest fidelity spectrum to date of a planetary-mass object.
VHS 1256 b is a 20 M widely separated (8\arcsec, a =
150 au), young, planetary-mass companion that shares photometric colors and
spectroscopic features with the directly imaged exoplanets HR 8799 c, d, and e.
As an L-to-T transition object, VHS 1256 b exists along the region of the
color-magnitude diagram where substellar atmospheres transition from cloudy to
clear. We observed VHS 1256~b with \textit{JWST}'s NIRSpec IFU and MIRI MRS
modes for coverage from 1 m to 20 m at resolutions of 1,000 -
3,700. Water, methane, carbon monoxide, carbon dioxide, sodium, and potassium
are observed in several portions of the \textit{JWST} spectrum based on
comparisons from template brown dwarf spectra, molecular opacities, and
atmospheric models. The spectral shape of VHS 1256 b is influenced by
disequilibrium chemistry and clouds. We directly detect silicate clouds, the
first such detection reported for a planetary-mass companion.Comment: Accepted ApJL Iterations of spectra reduced by the ERS team are
hosted at this link:
https://github.com/bemiles/JWST_VHS1256b_Reduction/tree/main/reduced_spectr
The JWST Early Release Science Program for Direct Observations of Exoplanetary Systems IV: NIRISS Aperture Masking Interferometry Performance and Lessons Learned
We present a performance analysis for the aperture masking interferometry
(AMI) mode on board the James Webb Space Telescope Near Infrared Imager and
Slitless Spectrograph (JWST/NIRISS). Thanks to self-calibrating observables,
AMI accesses inner working angles down to and even within the classical
diffraction limit. The scientific potential of this mode has recently been
demonstrated by the Early Release Science (ERS) 1386 program with a deep search
for close-in companions in the HIP 65426 exoplanetary system. As part of ERS
1386, we use the same dataset to explore the random, static, and calibration
errors of NIRISS AMI observables. We compare the observed noise properties and
achievable contrast to theoretical predictions. We explore possible sources of
calibration errors, and show that differences in charge migration between the
observations of HIP 65426 and point-spread function calibration stars can
account for the achieved contrast curves. Lastly, we use self-calibration tests
to demonstrate that with adequate calibration, NIRISS AMI can reach contrast
levels of mag. These tests lead us to observation planning
recommendations and strongly motivate future studies aimed at producing
sophisticated calibration strategies taking these systematic effects into
account. This will unlock the unprecedented capabilities of JWST/NIRISS AMI,
with sensitivity to significantly colder, lower mass exoplanets than
ground-based setups at orbital separations inaccessible to JWST coronagraphy.Comment: 20 pages, 12 figures, submitted to AAS Journal
The JWST Early Release Science Program for Direct Observations of Exoplanetary Systems V: Do Self-Consistent Atmospheric Models Represent JWST Spectra? A Showcase With VHS 1256 b
The unprecedented medium-resolution (R~1500-3500) near- and mid-infrared
(1-18um) spectrum provided by JWST for the young (140+/-20Myr) low-mass
(12-20MJup) L-T transition (L7) companion VHS1256b gives access to a catalogue
of molecular absorptions. In this study, we present a comprehensive analysis of
this dataset utilizing a forward modelling approach, applying our Bayesian
framework, ForMoSA. We explore five distinct atmospheric models to assess their
performance in estimating key atmospheric parameters: Teff, log(g), [M/H], C/O,
gamma, fsed, and R. Our findings reveal that each parameter's estimate is
significantly influenced by factors such as the wavelength range considered and
the model chosen for the fit. This is attributed to systematic errors in the
models and their challenges in accurately replicating the complex atmospheric
structure of VHS1256b, notably the complexity of its clouds and dust
distribution. To propagate the impact of these systematic uncertainties on our
atmospheric property estimates, we introduce innovative fitting methodologies
based on independent fits performed on different spectral windows. We finally
derived a Teff consistent with the spectral type of the target, considering its
young age, which is confirmed by our estimate of log(g). Despite the
exceptional data quality, attaining robust estimates for chemical abundances
[M/H] and C/O, often employed as indicators of formation history, remains
challenging. Nevertheless, the pioneering case of JWST's data for VHS1256b has
paved the way for future acquisitions of substellar spectra that will be
systematically analyzed to directly compare the properties of these objects and
correct the systematics in the models.Comment: 32 pages, 16 figures, 6 tables, 2 appendice
The \textit{JWST} Early Release Science Program for Direct Observations of Exoplanetary Systems III: Aperture Masking Interferometric Observations of the star HIP\,65426 at
We present aperture masking interferometry (AMI) observations of the star HIP
65426 at as a part of the \textit{JWST} Direct Imaging Early
Release Science (ERS) program obtained using the Near Infrared Imager and
Slitless Spectrograph (NIRISS) instrument. This mode provides access to very
small inner working angles (even separations slightly below the Michelson limit
of for an interferometer), which are inaccessible with the
classical inner working angles of the \textit{JWST} coronagraphs. When combined
with \textit{JWST}'s unprecedented infrared sensitivity, this mode has the
potential to probe a new portion of parameter space across a wide array of
astronomical observations. Using this mode, we are able to achieve a contrast
of \,mag relative to the host star at a separation
of {\sim}0.07\arcsec but detect no additional companions interior to the
known companion HIP\,65426\,b. Our observations thus rule out companions more
massive than 10{-}12\,\rm{M\textsubscript{Jup}} at separations
from HIP\,65426, a region out of reach of ground or
space-based coronagraphic imaging. These observations confirm that the AMI mode
on \textit{JWST} is sensitive to planetary mass companions orbiting at the
water frost line, even for more distant stars at 100\,pc. This result
will allow the planning and successful execution of future observations to
probe the inner regions of nearby stellar systems, opening essentially
unexplored parameter space.Comment: 15 pages, 9 figures, submitted to ApJ Letter
International genome-wide meta-analysis identifies new primary biliary cirrhosis risk loci and targetable pathogenic pathways.
Primary biliary cirrhosis (PBC) is a classical autoimmune liver disease for which effective immunomodulatory therapy is lacking. Here we perform meta-analyses of discovery data sets from genome-wide association studies of European subjects (n=2,764 cases and 10,475 controls) followed by validation genotyping in an independent cohort (n=3,716 cases and 4,261 controls). We discover and validate six previously unknown risk loci for PBC (Pcombined<5 × 10(-8)) and used pathway analysis to identify JAK-STAT/IL12/IL27 signalling and cytokine-cytokine pathways, for which relevant therapies exist
International genome-wide meta-analysis identifies new primary biliary cirrhosis risk loci and targetable pathogenic pathways
Robust estimation of bacterial cell count from optical density
Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data