40 research outputs found
Limb-darkening measurements for a cool red giant in microlensing event OGLE 2004-BLG-482
Aims: We present a detailed analysis of OGLE 2004-BLG-482, a relatively
high-magnification single-lens microlensing event which exhibits clear
extended-source effects. These events are relatively rare, but they potentially
contain unique information on the stellar atmosphere properties of their source
star, as shown in this study. Methods: Our dense photometric coverage of the
overall light curve and a proper microlensing modelling allow us to derive
measurements of the OGLE 2004-BLG-482 source star's linear limb-darkening
coefficients in three bands, including standard Johnson-Cousins I and R, as
well as in a broad clear filter. In particular, we discuss in detail the
problems of multi-band and multi-site modelling on the expected precision of
our results. We also obtained high-resolution UVES spectra as part of a ToO
programme at ESO VLT from which we derive the source star's precise fundamental
parameters. Results: From the high-resolution UVES spectra, we find that OGLE
2004-BLG-482's source star is a red giant of MK type a bit later than M3, with
Teff = 3667 +/- 150 K, log g = 2.1 +/- 1.0 and an assumed solar metallicity.
This is confirmed by an OGLE calibrated colour-magnitude diagram. We then
obtain from a detailed microlensing modelling of the light curve linear
limb-darkening coefficients that we compare to model-atmosphere predictions
available in the literature, and find a very good agreement for the I and R
bands. In addition, we perform a similar analysis using an alternative
description of limb darkening based on a principal component analysis of ATLAS
limb-darkening profiles, and also find a very good agreement between
measurements and model predictions.Comment: Accepted in A&
Full characterization of binary-lens event OGLE-2002-BLG-069 from PLANET observations
We analyze the photometric data obtained by PLANET and OGLE on the
caustic-crossing binary-lens microlensing event OGLE-2002-BLG-069. Thanks to
the excellent photometric and spectroscopic coverage of the event, we are able
to constrain the lens model up to the known ambiguity between close and wide
binary lenses. The detection of annual parallax in combination with
measurements of extended-source effects allows us to determine the mass,
distance and velocity of the lens components for the competing models. While
the model involving a close binary lens leads to a Bulge-Disc lens scenario
with a lens mass of M=(0.51 +- 0.15) M_sol and distance of D_L=(2.9 +- 0.4)
kpc, the wide binary lens solution requires a rather implausible binary
black-hole lens (M >=126 M_sol). Furthermore we compare current
state-of-the-art numerical and empirical models for the surface brightness
profile of the source, a G5III Bulge giant. We find that a linear
limb-darkening model for the atmosphere of the source star is consistent with
the data whereas a PHOENIX atmosphere model assuming LTE and with no free
parameter does not match our observations.Comment: 9 pages, 9 figures, accepted by A&
Structural analysis of underivatized neutral human milk oligosaccharides in the negative ion mode by nano-electrospray MSn (Part 1: Methodology)
Direct Evidence for the Presence of Human Milk Oligosaccharides in the Circulation of Breastfed Infants
Comparative transcriptomics reveals key differences in the response to milk oligosaccharides of infant gut-associated bifidobacteria
Breast milk enhances the predominance of Bifidobacterium species in the infant gut, probably due to its large concentration of human milk oligosaccharides (HMO). Here we screened infant-gut isolates of Bifidobacterium longum subsp. infantis and Bifidobacterium bifidum using individual HMO, and compared the global transcriptomes of representative isolates on major HMO by RNA-seq. While B. infantis displayed homogeneous HMO-utilization patterns, B. bifidum were more diverse and some strains did not use fucosyllactose (FL) or sialyllactose (SL). Transcriptomes of B. bifidum SC555 and B. infantis ATCC 15697 showed that utilization of pooled HMO is similar to neutral HMO, while transcriptomes for growth on FL were more similar to lactose than HMO in B. bifidum. Genes linked to HMO-utilization were upregulated by neutral HMO and SL, but not by FL in both species. In contrast, FL induced the expression of alternative gene clusters in B. infantis. Results also suggest that B. bifidum SC555 does not utilize fucose or sialic acid from HMO. Surprisingly, expression of orthologous genes differed between both bifidobacteria even when grown on identical substrates. This study highlights two major strategies found in Bifidobacterium species to process HMO, and presents detailed information on the close relationship between HMO and infant-gut bifidobacteria
mTOR Complex 1 Regulates Lipin 1 Localization to Control the SREBP Pathway
The nutrient- and growth factor-responsive kinase mTOR complex 1 (mTORC1) regulates many processes that control growth, including protein synthesis, autophagy, and lipogenesis. Through unknown mechanisms, mTORC1 promotes the function of SREBP, a master regulator of lipo- and sterolgenic gene transcription. Here, we demonstrate that mTORC1 regulates SREBP by controlling the nuclear entry of lipin 1, a phosphatidic acid phosphatase. Dephosphorylated, nuclear, catalytically active lipin 1 promotes nuclear remodeling and mediates the effects of mTORC1 on SREBP target gene, SREBP promoter activity, and nuclear SREBP protein abundance. Inhibition of mTORC1 in the liver significantly impairs SREBP function and makes mice resistant, in a lipin 1-dependent fashion, to the hepatic steatosis and hypercholesterolemia induced by a high-fat and -cholesterol diet. These findings establish lipin 1 as a key component of the mTORC1-SREBP pathway.National Institutes of Health (U.S.) (Grant R01 AI47389)National Institutes of Health (U.S.) (Grant R01 CA103866)LAM Foundation (Award)W. M. Keck Foundation (Award)American Diabetes Association (Fellowship)Virginia and D.K. Ludwig Fund for Cancer Research (Fellowship)Jane Coffin Childs Memorial Fund (Fellowship