65 research outputs found
Interaction Between Convection and Pulsation
This article reviews our current understanding of modelling convection
dynamics in stars. Several semi-analytical time-dependent convection models
have been proposed for pulsating one-dimensional stellar structures with
different formulations for how the convective turbulent velocity field couples
with the global stellar oscillations. In this review we put emphasis on two,
widely used, time-dependent convection formulations for estimating pulsation
properties in one-dimensional stellar models. Applications to pulsating stars
are presented with results for oscillation properties, such as the effects of
convection dynamics on the oscillation frequencies, or the stability of
pulsation modes, in classical pulsators and in stars supporting solar-type
oscillations.Comment: Invited review article for Living Reviews in Solar Physics. 88 pages,
14 figure
Asteroseismology and Interferometry
Asteroseismology provides us with a unique opportunity to improve our
understanding of stellar structure and evolution. Recent developments,
including the first systematic studies of solar-like pulsators, have boosted
the impact of this field of research within Astrophysics and have led to a
significant increase in the size of the research community. In the present
paper we start by reviewing the basic observational and theoretical properties
of classical and solar-like pulsators and present results from some of the most
recent and outstanding studies of these stars. We centre our review on those
classes of pulsators for which interferometric studies are expected to provide
a significant input. We discuss current limitations to asteroseismic studies,
including difficulties in mode identification and in the accurate determination
of global parameters of pulsating stars, and, after a brief review of those
aspects of interferometry that are most relevant in this context, anticipate
how interferometric observations may contribute to overcome these limitations.
Moreover, we present results of recent pilot studies of pulsating stars
involving both asteroseismic and interferometric constraints and look into the
future, summarizing ongoing efforts concerning the development of future
instruments and satellite missions which are expected to have an impact in this
field of research.Comment: Version as published in The Astronomy and Astrophysics Review, Volume
14, Issue 3-4, pp. 217-36
A Continuum of Cell States Spans Pluripotency and Lineage Commitment in Human Embryonic Stem Cells
Background: Commitment in embryonic stem cells is often depicted as a binary choice between alternate cell states, pluripotency and specification to a particular germ layer or extraembryonic lineage. However, close examination of human ES cell cultures has revealed significant heterogeneity in the stem cell compartment. Methodology/Principal Findings: We isolated subpopulations of embryonic stem cells using surface markers, then examined their expression of pluripotency genes and lineage specific transcription factors at the single cell level, and tested their ability to regenerate colonies of stem cells. Transcript analysis of single embryonic stem cells showed that there is a gradient and a hierarchy of expression of pluripotency genes in the population. Even cells at the top of the hierarchy generally express only a subset of the stem cell genes studied. Many cells co-express pluripotency and lineage specific genes. Cells along the continuum show a progressively decreasing likelihood of self renewal as their expression of stem cell surface markers and pluripotency genes wanes. Most cells that are positive for stem cell surface markers express Oct-4, but only those towards the top of the hierarchy express the nodal receptor TDGF-1 and the growth factor GDF3. Significance: These findings on gene expression in single embryonic stem cells are in concert with recent studies of early mammalian development, which reveal molecular heterogeneity and a stochasticity of gene expression in blastomeres. Our work indicates that only a small fraction of the population resides at the top of the hierarchy, that lineage priming (co-expression of stem cell and lineage specific genes) characterizes pluripotent stem cell populations, and that extrinsic signaling pathways are upstream of transcription factor networks that control pluripotency
Diversity of Staphylococcus aureus Isolates in European Wildlife
Staphylococcus aureus is a well-known colonizer and cause of infection among
animals and it has been described from numerous domestic and wild animal
species. The aim of the present study was to investigate the molecular
epidemiology of S. aureus in a convenience sample of European wildlife and to
review what previously has been observed in the subject field. 124 S. aureus
isolates were collected from wildlife in Germany, Austria and Sweden; they
were characterized by DNA microarray hybridization and, for isolates with
novel hybridization patterns, by multilocus sequence typing (MLST). The
isolates were assigned to 29 clonal complexes and singleton sequence types
(CC1, CC5, CC6, CC7, CC8, CC9, CC12, CC15, CC22, CC25, CC30, CC49, CC59, CC88,
CC97, CC130, CC133, CC398, ST425, CC599, CC692, CC707, ST890, CC1956, ST2425,
CC2671, ST2691, CC2767 and ST2963), some of which (ST2425, ST2691, ST2963)
were not described previously. Resistance rates in wildlife strains were
rather low and mecA-MRSA isolates were rare (n = 6). mecC-MRSA (n = 8) were
identified from a fox, a fallow deer, hares and hedgehogs. The common cattle-
associated lineages CC479 and CC705 were not detected in wildlife in the
present study while, in contrast, a third common cattle lineage, CC97, was
found to be common among cervids. No Staphylococcus argenteus or
Staphylococcus schweitzeri-like isolates were found. Systematic studies are
required to monitor the possible transmission of human- and livestock-
associated S. aureus/MRSA to wildlife and vice versa as well as the possible
transmission, by unprotected contact to animals. The prevalence of S.
aureus/MRSA in wildlife as well as its population structures in different
wildlife host species warrants further investigation
Longitudinal study on the association between three dietary indices, anthropometric parameters and blood lipids
Receptor Tyrosine Kinases in Osteosarcoma: 2019 Update
The primary conclusions of our 2014 contribution to this series were as follows:
Multiple receptor tyrosine kinases (RTKs) likely contribute to aggressive phenotypes in osteosarcoma and, therefore, inhibition of multiple RTKs is likely necessary for successful clinical outcomes.
Inhibition of multiple RTKs may also be useful to overcome resistance to inhibitors of individual RTKs as well as resistance to conventional chemotherapies.
Different combinations of RTKs are likely important in individual patients.
AXL, EPHB2, FGFR2, IGF1R, and RET were identified as promising therapeutic targets by our in vitro phosphoproteomic/siRNA screen of 42 RTKs in the highly metastatic LM7 and 143B human osteosarcoma cell lines.
This chapter is intended to provide an update on these topics as well as the large number of osteosarcoma clinical studies of inhibitors of multiple tyrosine kinases (multi-TKIs) that were recently published
Sorption Behavior of Selected Aldehyde-scavenging Agents in Poly(ethylene terephthalate) Blends
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