807 research outputs found
Ontmoeting met dementie
Dementie, een belangrijk maatschappelijk thema, waar K38 via kunst aandacht aan besteedt. Studenten van Academie Minerva hebben wekelijks, drie maanden lang, in het Groningse Odensehuis mensen met dementie geportretteerd. Deze expositie vormt een neerslag van hun ontmoeting
Quantum filter reduction for measurement-feedback control via unsupervised manifold learning
We derive simple models for the dynamics of a single atom coupled to a cavity
field mode in the absorptive bistable parameter regime by projecting the time
evolution of the state of the system onto a suitably chosen nonlinear
low-dimensional manifold, which is found by use of local tangent space
alignment. The output field from the cavity is detected with a homodyne
detector allowing observation of quantum jumps of the system between states
with different average numbers of photons in the cavity. We find that the
models, which are significantly faster to integrate numerically than the full
stochastic master equation, largely reproduce the dynamics of the system, and
we demonstrate that they are sufficiently accurate to facilitate feedback
control of the state of the system based on the predictions of the models
alone.Comment: 15 pages, 6 figure
The structures and total (minor + major) merger histories of massive galaxies up to z = 3 in the HST GOODS NICMOS Survey: A possible solution to the size evolution problem
We investigate the total major (> 1:4 by stellar mass) and minor (> 1:100 by
stellar mass) merger history of a population of 80 massive (M_* > 10^11 M_sol)
galaxies at high redshifts (z = 1.7 - 3). We utilize extremely deep and high
resolution HST H-band imaging from the GOODS NICMOS Survey (GNS), which
corresponds to rest-frame optical wavelengths at the redshifts probed. We find
that massive galaxies at high redshifts are often morphologically disturbed,
with a CAS deduced merger fraction f_m = 0.23 +/- 0.05 at z = 1.7 - 3. We find
close accord between close pair methods (within 30 kpc apertures) and CAS
methods for deducing major merger fractions at all redshifts. We deduce the
total (minor + major) merger history of massive galaxies with M_* > 10^9 M_sol
galaxies, and find that this scales roughly linearly with log-stellar-mass and
magnitude range. We test our close pair methods by utilizing mock galaxy
catalogs from the Millennium Simulation. We compute the total number of mergers
to be (4.5 +/- 2.9) / from z = 3 to the present, to a stellar mass
sensitivity threshold of ~ 1:100 (where \tau_m is the merger timescale in Gyr
which varies as a function of mass). This corresponds to an average mass
increase of (3.4 +/- 2.2) x 10^11 M_sol over the past 11.5 Gyrs due to merging.
We show that the size evolution observed for these galaxies may be mostly
explained by this merging.Comment: 19 pages, 10 figures, re-submitted to ApJ after a positive referee
report, originally submitted on Sept 20 201
Gas Accretion as a Dominant Formation Mode in Massive Galaxies from the GOODS NICMOS Survey
The ability to resolve all processes which drive galaxy formation is one of
the most fundamental goals in extragalactic astronomy. While star formation
rates and the merger history are now measured with increasingly high certainty,
the role of gas accretion from the intergalactic medium in supplying gas for
star formation still remains largely unknown. We present in this paper indirect
evidence for the accretion of gas into massive galaxies with initial stellar
masses M_*>10^{11} M_sol and following the same merger adjusted co-moving
number density at lower redshifts during the epoch 1.5 < z < 3, using results
from the GOODS NICMOS Survey (GNS). We show that the measured gas mass
fractions of these massive galaxies are inconsistent with the observed star
formation history for the same galaxy population. We further demonstrate that
this additional gas mass cannot be accounted for by cold gas delivered through
minor and major mergers. We also consider the effects of gas outflows and gas
recycling due to stellar evolution in these calculations. We argue that to
sustain star formation at the observed rates there must be additional methods
for increasing the cold gas mass, and that the likeliest method for
establishing this supply of gas is by accretion from the intergalactic medium.
We calculate that the average gas mass accretion rate into these massive
galaxies between 1.5 < z < 3.0, is \dot{M} = 96+/-19 M_sol/yr after accounting
for outflowing gas. We show that during this epoch, and for these very massive
galaxies, 49+/-20% of baryonic mass assembly is a result of gas accretion and
unresolved mergers. However, 66+/-20% of all star formation in this epoch is
the result of gas accretion. This reveals that for the most massive galaxies at
1.5< z< 3 gas accretion is the dominant method for instigating new stellar mass
assembly.Comment: MNRAS in press, 11 pages, 5 figure
Satellite Imagery to Map Topsoil Organic Carbon Content over Cultivated Areas: An Overview
There is a need to update soil maps and monitor soil organic carbon (SOC) in the upper horizons or plough layer for enabling decision support and land management, while complying with several policies, especially those favoring soil carbon storage. This review paper is dedicated to the satellite-based spectral approaches for SOC assessment that have been achieved from several satellite sensors, study scales and geographical contexts in the past decade. Most approaches relying on pure spectral models have been carried out since 2019 and have dealt with temperate croplands in Europe, China and North America at the scale of small regions, of some hundreds of km(2): dry combustion and wet oxidation were the analytical determination methods used for 50% and 35% of the satellite-derived SOC studies, for which measured topsoil SOC contents mainly referred to mineral soils, typically cambisols and luvisols and to a lesser extent, regosols, leptosols, stagnosols and chernozems, with annual cropping systems with a SOC value of similar to 15 g.kg(-1) and a range of 30 g.kg(-1) in median. Most satellite-derived SOC spectral prediction models used limited preprocessing and were based on bare soil pixel retrieval after Normalized Difference Vegetation Index (NDVI) thresholding. About one third of these models used partial least squares regression (PLSR), while another third used random forest (RF), and the remaining included machine learning methods such as support vector machine (SVM). We did not find any studies either on deep learning methods or on all-performance evaluations and uncertainty analysis of spatial model predictions. Nevertheless, the literature examined here identifies satellite-based spectral information, especially derived under bare soil conditions, as an interesting approach that deserves further investigations. Future research includes considering the simultaneous analysis of imagery acquired at several dates i.e., temporal mosaicking, testing the influence of possible disturbing factors and mitigating their effects fusing mixed models incorporating non-spectral ancillary information
A Spectral Transfer Function to Harmonize Existing Soil Spectral Libraries Generated by Different Protocols
Soil spectral libraries (SSLs) are important big-data archives (spectra associated with soil properties) that are analyzed via machine-learning algorithms to estimate soil attributes. Since different spectral measurement protocols are applied when constructing SSLs, it is necessary to examine harmonization techniques to merge the data. In recent years, several techniques for harmonization have been proposed, among which the internal soil standard (ISS) protocol is the most largely applied and has demonstrated its capacity to rectify systematic effects during spectral measurements. Here, we postulate that a spectral transfer function (TF) can be extracted between existing (old) SSLs if a subset of samples from two (or more) different SSLs are remeasured using the ISS protocol. A machine-learning TF strategy was developed, assembling random forest (RF) spectral-based models to predict the ISS spectral condition using soil samples from two existing SSLs. These SSLs had already been measured using different protocols without any ISS treatment the Brazilian (BSSL, generated in 2019) and the European (LUCAS, generated in 2009-2012) SSLs. To verify the TF's ability to improve the spectral assessment of soil attributes after harmonizing the different SSLs' protocols, RF spectral-based models for estimating organic carbon (OC) in soil were developed. The results showed high spectral similarities between the ISS and the ISS-TF spectral observations, indicating that post-ISS rectification is possible. Furthermore, after merging the SSLs with the TFs, the spectral-based assessment of OC was considerably improved, from R2 = 0.61, RMSE (g/kg) = 12.46 to R2 = 0.69, RMSE (g/kg) = 11.13. Given our results, this paper enhances the importance of soil spectroscopy by contributing to analyses in remote sensing, soil surveys, and digital soil mapping
A Deep Probe of the Galaxy Stellar Mass Functions at z~1-3 with the GOODS NICMOS Survey
We use a sample of 8298 galaxies observed in the HST GOODS NICMOS Survey
(GNS) to construct the galaxy stellar mass function as a function of both
redshift and stellar mass up to z=3.5 and down to masses of Mstar=10^8.5 Msun
at z~1. We discover that a significant fraction of all massive Mstar>10^11 Msun
galaxies are in place up to the highest redshifts we probe, with a decreasing
fraction of lower mass galaxies present at all redshifts. This is an example of
`galaxy mass downsizing', and is the result of massive galaxies forming before
lower mass ones, and not just simply ending their star formation earlier as in
traditional downsizing scenarios. We find that the faint end slope is
significantly steeper than what is found in previous investigations. We
demonstrate that this steeper mass function better matches the stellar mass
added due to star formation, thereby alleviating some of the mismatch between
these two measures of the evolution of galaxy mass. We furthermore examine the
stellar mass function divided into blue/red systems, as well as for star
forming and non-star forming galaxies. We find a similar mass downsizing
present for both blue/red and star-forming/non-star forming galaxies, and that
the low mass galaxies are mostly all blue, and are therefore creating the steep
mass functions. We furthermore show that, although there is a downsizing such
that high mass galaxies are nearer their z=0 values at high redshift, this
turns over at masses Mstar~10^10 Msun, such that the lowest mass galaxies are
more common than galaxies at slight higher masses, creating a `dip' in the
observed galaxy mass function. We argue that the galaxy assembly process may be
driven by different mechanisms at low and high masses, and that the efficiency
of the galaxy formation process is lowest at masses Mstar~10^10 Msun at 1<z<3.
(Abridged)Comment: 16 pages, 11 figures, MNRAS, accepte
Timed written picture naming in 14 european languages
We describe the Multilanguage Written Picture Naming Dataset. This gives trial-level data and time and agreement norms for written naming of the 260 pictures of everyday objects that compose the colorized Snodgrass and Vanderwart picture set (Rossion & Pourtois in Perception, 33, 217\u2013236, 2004). Adult participants gave keyboarded responses in their first language under controlled experimental conditions (N = 1,274, with subsamples responding in Bulgarian, Dutch, English, Finnish, French, German, Greek, Icelandic, Italian, Norwegian, Portuguese, Russian, Spanish, and Swedish). We measured the time to initiate a response (RT) and interkeypress intervals, and calculated measures of name and spelling agreement. There was a tendency across all languages for quicker RTs to pictures with higher familiarity, image agreement, and name frequency, and with higher name agreement. Effects of spelling agreement and effects on output rates after writing onset were present in some, but not all, languages. Written naming therefore shows name retrieval effects that are similar to those found in speech, but our findings suggest the need for cross-language comparisons as we seek to understand the orthographic retrieval and/or assembly processes that are specific to written output
Stromal Hedgehog signalling is downregulated in colon cancer and its restoration restrains tumour growth
A role for Hedgehog (Hh) signalling in the development of colorectal cancer
(CRC) has been proposed. In CRC and other solid tumours, Hh ligands are
upregulated; however, a specific Hh antagonist provided no benefit in a
clinical trial. Here we use Hh reporter mice to show that downstream Hh
activity is unexpectedly diminished in a mouse model of colitis-associated
colon cancer, and that downstream Hh signalling is restricted to the stroma.
Functionally, stroma-specific Hh activation in mice markedly reduces the
tumour load and blocks progression of advanced neoplasms, partly via the
modulation of BMP signalling and restriction of the colonic stem cell
signature. By contrast, attenuated Hh signalling accelerates colonic
tumourigenesis. In human CRC, downstream Hh activity is similarly reduced and
canonical Hh signalling remains predominantly paracrine. Our results suggest
that diminished downstream Hh signalling enhances CRC development, and that
stromal Hh activation can act as a colonic tumour suppressor
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