43 research outputs found
Glauconitic deposits at Julegård on the south coast of Bornholm, Denmark dated to the Cambrian
Collisional Stripping and Disruption of Super-Earths
The final stage of planet formation is dominated by collisions between
planetary embryos. The dynamics of this stage determine the orbital
configuration and the mass and composition of planets in the system. In the
solar system, late giant impacts have been proposed for Mercury, Earth, Mars,
and Pluto. In the case of Mercury, this giant impact may have significantly
altered the bulk composition of the planet. Here we present the results of
smoothed particle hydrodynamics simulations of high-velocity (up to ~5 v_esc)
collisions between 1 and 10 M_Earth planets of initially terrestrial
composition to investigate the end stages of formation of extrasolar
super-Earths. As found in previous simulations of collisions between smaller
bodies, when collision energies exceed simple merging, giant impacts are
divided into two regimes: (1) disruption and (2) hit-and-run (a grazing
inelastic collision and projectile escape). Disruption occurs when the impact
parameter is near zero, when the projectile mass is small compared to the
target, or at extremely high velocities. In the disruption regime, we derive
the criteria for catastrophic disruption (when half the total colliding mass is
lost), the transition energy between accretion and erosion, and a scaling law
for the change in bulk composition (iron-to-silicate ratio) resulting from
collisional stripping of a mantle.Comment: 10 pages, 1 table, 4 figures. Accepted for publication in ApJ Letter
PulseSatellite: A tool using human-AI feedback loops for satellite image analysis in humanitarian contexts
Humanitarian response to natural disasters and conflicts can be assisted by
satellite image analysis. In a humanitarian context, very specific satellite
image analysis tasks must be done accurately and in a timely manner to provide
operational support. We present PulseSatellite, a collaborative satellite image
analysis tool which leverages neural network models that can be retrained
on-the fly and adapted to specific humanitarian contexts and geographies. We
present two case studies, in mapping shelters and floods respectively, that
illustrate the capabilities of PulseSatellite.Comment: 2 pages, 2 figure
S’Estret des Temps: registro cuaternario, eolianitas y estructuras asociadas
Abstract not availabl
Bifunctionality of a biofilm matrix protein controlled by redox state
Significance
The biofilm matrix is a critical target in the hunt for novel strategies to destabilize or stabilize biofilms. Knowledge of the processes controlling matrix assembly is therefore an essential prerequisite to exploitation. Here, we highlight that the complexity of the biofilm matrix is even higher than anticipated, with one matrix component making two independent functional contributions to the community. The influence the protein exerts is dependent on the local environmental properties, providing another dimension to consider during analysis. These findings add to the evidence that bacteria can evolve multifunctional uses for the extracellular matrix components.</jats:p
A Semi-Analytic Model for the Co-evolution of Galaxies, Black Holes, and Active Galactic Nuclei
We present a new semi-analytic model that self-consistently traces the growth
of supermassive black holes (BH) and their host galaxies within the context of
the LCDM cosmological framework. In our model, the energy emitted by accreting
black holes regulates the growth of the black holes themselves, drives galactic
scale winds that can remove cold gas from galaxies, and produces powerful jets
that heat the hot gas atmospheres surrounding groups and clusters. We present a
comprehensive comparison of our model predictions with observational
measurements of key physical properties of low-redshift galaxies, such as cold
gas fractions, stellar metallicities and ages, and specific star formation
rates. We find that our new models successfully reproduce the exponential
cutoff in the stellar mass function and the stellar and cold gas mass densities
at z~0, and predict that star formation should be largely, but not entirely,
quenched in massive galaxies at the present day. We also find that our model of
self-regulated BH growth naturally reproduces the observed relation between BH
mass and bulge mass. We explore the global formation history of galaxies in our
models, presenting predictions for the cosmic histories of star formation,
stellar mass assembly, cold gas, and metals. We find that models assuming the
"concordance" LCDM cosmology overproduce star formation and stellar mass at
high redshift (z>2). A model with less small-scale power predicts less star
formation at high redshift, and excellent agreement with the observed stellar
mass assembly history, but may have difficulty accounting for the cold gas in
quasar absorption systems at high redshift (z~3-4).Comment: MNRAS accepte
Malignant inflammation in cutaneous T-cell lymphoma: a hostile takeover
Cutaneous T-cell lymphomas (CTCL) are characterized by the presence of chronically inflamed skin lesions containing malignant T cells. Early disease presents as limited skin patches or plaques and exhibits an indolent behavior. For many patients, the disease never progresses beyond this stage, but in approximately one third of patients, the disease becomes progressive, and the skin lesions start to expand and evolve. Eventually, overt tumors develop and the malignant T cells may disseminate to the blood, lymph nodes, bone marrow, and visceral organs, often with a fatal outcome. The transition from early indolent to progressive and advanced disease is accompanied by a significant shift in the nature of the tumor-associated inflammation. This shift does not appear to be an epiphenomenon but rather a critical step in disease progression. Emerging evidence supports that the malignant T cells take control of the inflammatory environment, suppressing cellular immunity and anti-tumor responses while promoting a chronic inflammatory milieu that fuels their own expansion. Here, we review the inflammatory changes associated with disease progression in CTCL and point to their wider relevance in other cancer contexts. We further define the term "malignant inflammation" as a pro-tumorigenic inflammatory environment orchestrated by the tumor cells and discuss some of the mechanisms driving the development of malignant inflammation in CTCL
Distinctive subgroups derived by cluster analysis based on pain and psychological symptoms in Swedish older adults with chronic pain – a population study (PainS65+)
Sarcopenia; Aging-related loss of muscle mass and function
Sarcopenia is a loss of muscle mass and function in the elderly that reduces mobility, diminishes quality of life, and can lead to fall-related injuries, which require costly hospitalization and extended rehabilitation. This review focuses on the aging-related structural changes and mechanisms at cellular and subcellular levels underlying changes in the individual motor unit: specifically, the perikaryon of -motoneuron, its neuromuscular junction(s), and the muscle fibers that it innervates. Loss of muscle mass with aging, which is largely due to the progressive loss of motoneurons, is associated with reduced muscle fiber number and size. Muscle function progressively declines because motoneuron loss is not adequately compensated by reinnervation of muscle fibers by the remaining motoneurons. At the intracellular level, key factors are qualitative changes in posttranslational modifications of muscle proteins and the loss of coordinated control between contractile, mitochondrial, and sarcoplasmic reticulum protein expression. Quantitative and qualitative changes in skeletal muscle during the process of aging also have been implicated in the pathogenesis of acquired and hereditary neuromuscular disorders. In experimental models, specific intervention strategies have shown encouraging results on limiting deterioration of motor unit structure and function under conditions of impaired innervation. Translated to the clinic, if these or similar interventions, by saving muscle and improving mobility, could help alleviate sarcopenia in the elderly, there would be both great humanitarian benefits and large cost savings for health care systems