75 research outputs found
Elucidating the photosynthetic responses in chlorophyll-deficient soybean (Glycine max, L.) leaf
Chlorophyll (Chl)-deficient plants can potentially increase global surface albedo of mono-cropping systems, and simultaneously maintain a similar photosynthetic efficiency by increasing light canopy penetration and thus lowering investment in pigments. However, some previous studies have shown that pale mutants might reduce productivity in field conditions. Such lower yields were suspected to be due to loss of photosynthetic efficiency at leaf level during light fluctuations as a consequence of reduced capacity and slower relaxation of non-photochemical quenching (NPQ) of Chl fluorescence. In this paper, we tested this hypothesis by comparing, CO2 assimilation (A), photosystem II (PSII) efficiency (ΊPSII), photochemical quenching and NPQ, electron transport rate (ETR) and fluorescence yield (Fyield) in a green soybean (Glycine max L.) cultivar (Eiko) and in a Chl-deficient (MinnGold) mutant under dynamically fluctuating light conditions. MinnGold had significantly slower induction of ETR and lower A and ETR than Eiko, but there was little difference in ΊPSII between the two genotypes, suggesting that the lower photosynthesis of MinnGold was mainly due to lower light energy absorption by a Chl-deficient leaf. The NPQ capacity was also smaller in MinnGold than in Eiko. As for the kinetics of the rapidly inducible component of NPQ, MinnGold showed slower induction, not relaxation, than Eiko. The combination of the effect of Chl-deficiency on lower photosynthesis, NPQ capacity and slower NPQ induction may explain the lower biomass accumulation of MinnGold in the field. Our physiological observations, combined with fluorescence kinetics, can serve as a basis to parameterize Chl content in modelling radiative transfer and photosynthesis for upscaling measures of plant and ecosystem productivity by a big leaf model
Spontaneous phase oscillation induced by inertia and time delay
We consider a system of coupled oscillators with finite inertia and
time-delayed interaction, and investigate the interplay between inertia and
delay both analytically and numerically. The phase velocity of the system is
examined; revealed in numerical simulations is emergence of spontaneous phase
oscillation without external driving, which turns out to be in good agreement
with analytical results derived in the strong-coupling limit. Such
self-oscillation is found to suppress synchronization and its frequency is
observed to decrease with inertia and delay. We obtain the phase diagram, which
displays oscillatory and stationary phases in the appropriate regions of the
parameters.Comment: 5 pages, 6 figures, to pe published in PR
The Frontier Fields Lens Modeling Comparison Project
Gravitational lensing by clusters of galaxies offers a powerful probe of
their structure and mass distribution. Deriving a lens magnification map for a
galaxy cluster is a classic inversion problem and many methods have been
developed over the past two decades to solve it. Several research groups have
developed techniques independently to map the predominantly dark matter
distribution in cluster lenses. While these methods have all provided
remarkably high precision mass maps, particularly with exquisite imaging data
from the Hubble Space Telescope (HST), the reconstructions themselves have
never been directly compared. In this paper, we report the results of comparing
various independent lens modeling techniques employed by individual research
groups in the community. Here we present for the first time a detailed and
robust comparison of methodologies for fidelity, accuracy and precision. For
this collaborative exercise, the lens modeling community was provided simulated
cluster images -- of two clusters Ares and Hera -- that mimic the depth and
resolution of the ongoing HST Frontier Fields. The results of the submitted
reconstructions with the un-blinded true mass profile of these two clusters are
presented here. Parametric, free-form and hybrid techniques have been deployed
by the participating groups and we detail the strengths and trade-offs in
accuracy and systematics that arise for each methodology. We note in conclusion
that lensing reconstruction methods produce reliable mass distributions that
enable the use of clusters as extremely valuable astrophysical laboratories and
cosmological probes.Comment: 38 pages, 25 figures, submitted to MNRAS, version with full
resolution images can be found at
http://pico.bo.astro.it/~massimo/papers/FFsims.pd
A MUSE view of the massive merging galaxy cluster ACT-CL J0102-4915 (El Gordo) at z = 0.87: robust strong lensing model and data release
We present a detailed strong lensing analysis of the massive and distant
() galaxy cluster ACT-CL J01024915 (ACT0102, also known as El
Gordo), taking advantage of new spectroscopic data from the Multi Unit
Spectroscopic Explorer (MUSE) on the Very Large Telescope, and archival imaging
from the Hubble Space Telescope. Thanks to the MUSE data, we measure secure
redshifts for 374 single objects, including 23 multiply lensed galaxies, and
167 cluster members of ACT0102. The observed positions of 56 multiple images,
along with their new spectroscopic redshift measurements, are used as
constraints for our strong lensing model. Remarkably, some multiple images are
detected out to a large projected distance of Mpc from the
brightest cluster galaxy, allowing us to estimate a projected total mass value
of within that radius. We
find that we need two extended cluster mass components, the mass contributions
from the cluster members and the additional lensing effect of a foreground
() group of galaxies, to predict the positions of all multiple images
with a root mean square offset of . The main cluster-scale mass
component is centered very closely to the brightest cluster galaxy and the
other extended mass component is located in the north-west region of the
cluster. These two mass components have very similar values of mass projected
within 300 kpc from their centers, namely
and
, in agreement with the major
merging scenario of ACT0102. We make publicly available the lens model,
including the magnification maps and posterior distributions of the model
parameter values, as well as the full spectroscopic catalogue containing all
redshift measurements obtained with MUSE.Comment: 12 pages, 9 figures, 4 tables + appendix. Submitted to A&
Partially and Fully Frustrated Coupled Oscillators With Random Pinning Fields
We have studied two specific models of frustrated and disordered coupled
Kuramoto oscillators, all driven with the same natural frequency, in the
presence of random external pinning fields. Our models are structurally
similar, but differ in their degree of bond frustration and in their finite
size ground state properties (one has random ferro- and anti-ferromagnetic
interactions; the other has random chiral interactions). We have calculated the
equilibrium properties of both models in the thermodynamic limit using the
replica method, with emphasis on the role played by symmetries of the pinning
field distribution, leading to explicit predictions for observables,
transitions, and phase diagrams. For absent pinning fields our two models are
found to behave identically, but pinning fields (provided with appropriate
statistical properties) break this symmetry. Simulation data lend satisfactory
support to our theoretical predictions.Comment: 37 pages, 7 postscript figure
Dynamics of sun-induced chlorophyll fluorescence and reflectance to detect stress-induced variations in canopy photosynthesis
Passive measurement of sun-induced chlorophyll fluorescence (F) represents the most promising tool to quantify changes in photosynthetic functioning on a large scale. However, the complex relationship between this signal and other photosynthesis-related processes restricts its interpretation under stress conditions. To address this issue, we conducted a field campaign by combining daily airborne and ground-based measurements of F (normalized to photosynthetically active radiation), reflectance and surface temperature and related the observed changes to stress-induced variations in photosynthesis. A lawn carpet was sprayed with different doses of the herbicide Dicuran. Canopy-level measurements of gross primary productivity indicated dosage-dependent inhibition of photosynthesis by the herbicide. Dosage-dependent changes in normalized F were also detected. After spraying, we first observed a rapid increase in normalized F and in the Photochemical Reflectance Index, possibly due to the blockage of electron transport by Dicuran and the resultant impairment of xanthophyll-mediated non-photochemical quenching. This initial increase was followed by a gradual decrease in both signals, which coincided with a decline in pigment-related reflectance indices. In parallel, we also detected a canopy temperature increase after the treatment. These results demonstrate the potential of using F coupled with relevant reflectance indices to estimate stress-induced changes in canopy photosynthesis
WNT signalling in prostate cancer
Genome sequencing and gene expression analyses of prostate tumours have highlighted the potential importance of genetic and epigenetic changes observed in WNT signalling pathway components in prostate tumours-particularly in the development of castration-resistant prostate cancer. WNT signalling is also important in the prostate tumour microenvironment, in which WNT proteins secreted by the tumour stroma promote resistance to therapy, and in prostate cancer stem or progenitor cells, in which WNT-ÎČ-catenin signals promote self-renewal or expansion. Preclinical studies have demonstrated the potential of inhibitors that target WNT receptor complexes at the cell membrane or that block the interaction of ÎČ-catenin with lymphoid enhancer-binding factor 1 and the androgen receptor, in preventing prostate cancer progression. Some WNT signalling inhibitors are in phase I trials, but they have yet to be tested in patients with prostate cancer
The Extended [C ii] under Construction? Observation of the Brightest High-z Lensed Star-forming Galaxy at z = 6.2
We present results of [C ii] 158 ÎŒm emission line observations, and report the spectroscopic redshift confirmation of a strongly lensed (ÎŒ ⌠20) star-forming galaxy, MACS0308-zD1 at z = 6.2078 ± 0.0002. The [C ii] emission line is detected with a signal-to-noise ratio >6 within the rest-frame UV-bright clump of the lensed galaxy (zD1.1) and exhibits multiple velocity components; the narrow [C ii] has a velocity full width half maximum (FWHM) of 110 ± 20 km sâ1, while broader [C ii] is seen with an FWHM of 230 ± 50 km sâ1. The broader [C ii] component is blueshifted (â80 ± 20 km sâ1) with respect to the narrow [C ii] component, and has a morphology that extends beyond the UV-bright clump. We find that, while the narrow [C ii] emission is most likely associated with zD1.1, the broader component is possibly associated with a physically distinct gas component from zD1.1 (e.g., outflowing or inflowing gas). Based on the nondetection of λ158ÎŒm dust continuum, we find that MACS0308-zD1's star formation activity occurs in a dust-free environment indicated by a strong upper limit of infrared luminosity âČ9 Ă 108Lâ. Targeting this strongly lensed faint galaxy for follow-up Atacama Large Millimeter/submillimeter Array and JWST observations will be crucial to characterize the details of typical galaxy growth in the early Universe
BUFFALO/Flashlights: Constraints on the abundance of lensed supergiant stars in the Spock galaxy at redshift 1
In this work, we present a constraint on the abundance of supergiant (SG) stars at redshift z â 1, based on recent observations of astrongly lensed arc at this redshift. First we derived a free-form model of MACS J0416.1-2403 using data from the Beyond Ultradeep Frontier Fields and Legacy Observations (BUFFALO) program. The new lens model is based on 72 multiply lensed galaxies thatproduce 214 multiple images, making it the largest sample of spectroscopically confirmed lensed galaxies on this cluster. The largercoverage in BUFFALO allowed us to measure the shear up to the outskirts of the cluster, and extend the range of lensing constraintsup to âŒ1 Mpc from the central region, providing a mass estimate up to this radius. As an application, we make predictions for thenumber of high-redshift multiply lensed galaxies detected in future observations with the James Webb Space Telescope (JWST).Then we focus on a previously known lensed galaxy at z = 1.0054, nicknamed Spock, which contains four previously reportedtransients. We interpret these transients as microcaustic crossings of SG stars and explain how we computed the probability of suchevents. Based on simplifications regarding the stellar evolution, we find that microlensing (by stars in the intracluster medium) ofSG stars at z = 1.0054 can fully explain these events. The inferred abundance of SG stars is consistent with either (1) a numberdensity of stars with bolometric luminosities beyond the Humphreys-Davidson (HD) limit (Lmax â 6 Ă 105 L for red stars), whichis below âŒ400 stars kpcâ2, or (2) the absence of stars beyond the HD limit but with a SG number density of âŒ9000 kpcâ2 for starswith luminosities between 105 L and 6 Ă 105 L. This is equivalent to one SG star per 10 Ă 10 pc2. Finally, we make predictions forfuture observations with JWSTâs NIRcam. We find that in observations made with the F200W filter that reach 29 mag AB, if cool red SG stars exist at z â 1 beyond the HD limit, they should be easily detected in this arc
BUFFALO/Flashlights: Constraints on the abundance of lensed supergiant stars in the Spock galaxy at redshift 1
We present a constraint on the abundance of supergiant (SG) stars at redshift
z approx. 1, based on recent observations of a strongly lensed arc at this
redshift. First we derive a free-form model of MACS J0416.1-2403 using data
from the BUFFALO program. The new lens model is based on 72 multiply lensed
galaxies that produce 214 multiple images, making it the largest sample of
spectroscopically confirmed lensed galaxies on this cluster. The larger
coverage in BUFFALO allows us to measure the shear up to the outskirts of the
cluster, and extend the range of lensing constraints up to ~ 1 Mpc from the
central region, providing a mass estimate up to this radius. As an application,
we make predictions for the number of high-redshift multiply-lensed galaxies
detected in future observations with JWST. Then we focus on a previously known
lensed galaxy at z=1.0054, nicknamed Spock, which contains four previously
reported transients. We interpret these transients as microcaustic crossings of
SG stars and compute the probability of such events. Based on simplifications
regarding the stellar evolution, we find that microlensing (by stars in the
intracluster medium) of SG stars at z=1.0054 can fully explain these events.
The inferred abundance of SG stars is consistent with either (1) a number
density of stars with bolometric luminosities beyond the Humphreys-Davidson
(HD) limit (L ~ ) that is below 400 stars per sq. kpc,
or (2) the absence of stars beyond the HD limit but with a SG number density of
~ 9000 per sq. kpc for stars with luminosities between and
. This is equivalent to one SG star per 10x10 pc. We finally
make predictions for future observations with JWST's NIRcam. We find that in
observations made with the F200W filter that reach 29 mag AB, if cool red SG
stars exist at z~1 beyond the HD limit, they should be easily detected in this
arcComment: 24 pages & 18 figure
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