246 research outputs found
Minimal decoherence from inflation
We compute the rate with which super-Hubble cosmological fluctuations are
decohered during inflation, by their gravitational interactions with unobserved
shorter-wavelength scalar and tensor modes. We do so using Open Effective Field
Theory methods, that remain under control at the late times of observational
interest, contrary to perturbative calculations. Our result is minimal in the
sense that it only incorporates the self-interactions predicted by General
Relativity in single-clock models (additional interaction channels should only
speed up decoherence). We find that decoherence is both suppressed by the first
slow-roll parameter and by the energy density during inflation in Planckian
units, but that it is enhanced by the volume comprised within the scale of
interest, in Hubble units. This implies that, for the scales probed in the
Cosmic Microwave Background, decoherence is effective as soon as inflation
proceeds above GeV. Alternatively, if inflation proceeds
at GUT scale decoherence is incomplete only for the scales crossing out the
Hubble radius in the last ~ 13 e-folds, of inflation. We also compute how
short-wavelength scalar modes decohere primordial tensor perturbations, finding
a faster rate unsuppressed by slow-roll parameters. Identifying the parametric
dependence of decoherence, and the rate at which it proceeds, helps suggest
ways to look for quantum effects.Comment: 31 pages + appendices, 7 figure
Evolution of carbonated lacustrine environment with stromatolites : a paleoecological approach (quarry of Montaigu-le-Blin, Limagne graben, Allier, France)
La carriĂšre de Montaigu-le-Blin, situĂ©e en Limagne bourbonnaise permet dâanalyser en dĂ©tail la sĂ©dimentation
lacustre aquitanienne et de reconstituer les environnements de dépÎt. Les sédiments marneux et calcaires renferment
une faune dâeau douce et une flore particuliĂšrement dĂ©veloppĂ©es. Les dĂ©pĂŽts sĂ©dimentaires traduisent des
variations pĂ©riodiques du niveau de la tranche dâeau qui provoquent aussi des variations pĂ©riodiques des conditions chimiques
au sein du lac. Ils sont représentatifs de milieux alternativement anoxiques et oxygénés. Ces variations sont le
rĂ©sultat dâalternances de pĂ©riodes dâhumiditĂ© variable, et seraient donc dâorigine climatique. Ces alternances ont provoquĂ©
des variations pĂ©riodiques des assemblages floro-fauniques : des thanatocĆnoses surviennent durant les pĂ©riodes
anoxiques, alors que le développement majeur des algues encroûtantes responsables de la formation de concrétions algaires,
apparaĂźt lors des pĂ©riodes oxygĂ©nĂ©es. Ces pĂ©riodes sont Ă©galement marquĂ©es par une augmentation de lâhydrodynamisme,
associée à des apports détritiques du bassin versant. Les stromatolithes présents dans le milieu montrent des
morphologies trÚs variées, tributaires des associations de flore et de faune (algues, bactéries, fourreaux de larves de TrichoptÚres)
qui les composent, ainsi que de leur milieu de croissance. Les associations de stromatolithes forment des
complexes plurimĂ©triques que lâon propose de situer par rapport Ă un palĂ©orivage
Reshaping the tumor stroma for treatment of pancreatic cancer
Pancreatic cancer is accompanied by a fibrotic reaction that alters interactions between tumor cells and the stroma to promote tumor progression. Consequently, strategies to target the tumor stroma might be used to treat patients with pancreatic cancer. We review recently developed approaches for reshaping the pancreatic tumor stroma and discuss how these might improve patient outcomes. We also describe relationships between the pancreatic tumor extracellular matrix, the vasculature, the immune system, and metabolism, and discuss the implications for the development of stromal compartmentâspecific therapies
Cosmological Inflation and the Quantum Measurement Problem
According to cosmological inflation, the inhomogeneities in our universe are
of quantum mechanical origin. This scenario is phenomenologically very
appealing as it solves the puzzles of the standard hot big bang model and
naturally explains why the spectrum of cosmological perturbations is almost
scale invariant. It is also an ideal playground to discuss deep questions among
which is the quantum measurement problem in a cosmological context. Although
the large squeezing of the quantum state of the perturbations and the
phenomenon of decoherence explain many aspects of the quantum to classical
transition, it remains to understand how a specific outcome can be produced in
the early universe, in the absence of any observer. The Continuous Spontaneous
Localization (CSL) approach to quantum mechanics attempts to solve the quantum
measurement question in a general context. In this framework, the wavefunction
collapse is caused by adding new non linear and stochastic terms to the
Schroedinger equation. In this paper, we apply this theory to inflation, which
amounts to solving the CSL parametric oscillator case. We choose the
wavefunction collapse to occur on an eigenstate of the Mukhanov-Sasaki variable
and discuss the corresponding modified Schroedinger equation. Then, we compute
the power spectrum of the perturbations and show that it acquires a universal
shape with two branches, one which remains scale invariant and one with nS=4, a
spectral index in obvious contradiction with the Cosmic Microwave Background
(CMB) anisotropy observations. The requirement that the non-scale invariant
part be outside the observational window puts stringent constraints on the
parameter controlling the deviations from ordinary quantum mechanics...
(Abridged).Comment: References added, minor corrections, conclusions unchange
CAF subpopulations: a new reservoir of stromal targets in pancreatic cancer
Cancer-associated fibroblasts (CAFs) are one of the most significant components in the tumour microenvironment (TME), where they can perform several protumourigenic functions. Several studies have recently reported that CAFs are more heterogenous and plastic than was previously thought. As such, there has been a shift in the field to study CAF subpopulations and the emergent functions of these subsets in tumourigenesis. In this review, we explore how different aspects of CAF heterogeneity are defined and how these manifest in multiple cancers, with a focus on pancreatic ductal adenocarcinoma (PDAC). We also discuss therapeutic approaches to selectively target protumourigenic CAF functions, while avoiding normal fibroblasts, providing insight into the future of stromal targeting for the treatment of PDAC and other solid tumours
Influence of basement heterogeneity on the architecture of low subsidence rate Paleozoic intracratonic basins (Reggane, Ahnet, Mouydir and Illizi basins, Hoggar Massif)
The Paleozoic intracratonic North African Platform is characterized by an
association of arches (ridges, domes, swells, or paleo-highs) and low
subsidence rate syncline basins of different wavelengths (75â620 km). The
Reggane, Ahnet, Mouydir and Illizi basins are successively delimited from
east to west by the Amguid El Biod, Arak-Foum Belrem, and Azzel Matti arches.
Through the analysis of new unpublished geological data (i.e., satellite
images, well logs, seismic lines), the deposits associated with these arches
and syncline basins exhibit thickness variations and facies changes ranging
from continental to marine environments. The arches are characterized by thin
amalgamated deposits with condensed and erosional surfaces, whereas the
syncline basins exhibit thicker and well-preserved successions. In addition,
the vertical facies succession evolves from thin Silurian to Givetian
deposits into thick Upper Devonian sediments. Synsedimentary structures and
major unconformities are related to several tectonic events such as the
CambrianâOrdovician extension, the OrdovicianâSilurian glacial rebound,
the SilurianâDevonian Caledonian extension/compression, the late Devonian
extension/compression, and the Hercynian compression. Locally, deformation is
characterized by near-vertical planar normal faults responsible for horst and
graben structuring associated with folding during the
CambrianâOrdovicianâSilurian period. These structures may have been
inverted or reactivated during the Devonian (i.e., Caledonian, MidâLate
Devonian) compression and the Carboniferous (i.e., pre-Hercynian to
Hercynian). Additionally, basement characterization from geological and
geophysics data (aeromagnetic and gravity maps), shows an interesting
age-dependent zonation of the terranes which are bounded by mega-shear zones
within the archesâbasins framework. The old terranes are situated under
arches while the young terranes are located under the basins depocenter.
This structural framework results from the accretion of Archean and
Proterozoic terranes inherited from former orogeny (e.g., Pan-African orogeny
900â520 Ma). Therefore, the sedimentary infilling pattern and the nature of
deformation result from the repeated slow Paleozoic reactivation of
Precambrian terranes bounded by subvertical lithospheric fault systems.
Alternating periods of tectonic quiescence and low-rate subsidence
acceleration associated with extension and local inversion tectonics
correspond to a succession of Paleozoic geodynamic events (i.e., far-field
orogenic belt, glaciation).</p
Intravital FRAP imaging using an E-cadherin-GFP mouse reveals disease- and drug-dependent dynamic regulation of cell-cell junctions in live tissue
E-cadherin-mediated cell-cell junctions play a prominent role in maintaining the epithelial architecture. The disruption or deregulation of these adhesions in cancer can lead to the collapse of tumor epithelia that precedes invasion and subsequent metastasis. Here we generated an E-cadherin-GFP mouse that enables intravital photobleaching and
quantification of E-cadherin mobility in live tissue without affecting normal biology. We demonstrate the broad applications of this mouse by examining
E-cadherin regulation in multiple tissues, including mammary, brain, liver, and kidney tissue, while specifically monitoring E-cadherin mobility during
disease progression in the pancreas. We assess E-cadherin stability in native pancreatic tissue upon genetic manipulation involving Kras and p53
or in response to anti-invasive drug treatment and gain insights into the dynamic remodeling of E-cadherin during in situ cancer progression. FRAP in the E-cadherin-GFP mouse, therefore, promises to be a valuable tool to fundamentally expand our understanding of E-cadherin-mediated events in native microenvironments
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