66 research outputs found
Silencing of FGF ‐21 expression promotes hepatic gluconeogenesis and glycogenolysis by regulation of the STAT 3– SOCS 3 signal
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/106851/1/febs12767.pd
Interacting coronae of two T Tauri stars: first observational evidence for solar-like helmet streamers
Context {The young binary system V773 Tau A exhibits a persistent radio
flaring activity that gradually increases from a level of a few mJy at
apoastron to more than 100 mJy at periastron. Interbinary collisions between
very large (> 15 R) magnetic structures anchored on the two rotating stars of
the system have been proposed to be the origin of these periodic radio flares.
Magnetic structures extended over tens of stellar radii, that can also account
for the observed fast decay of the radio flares, seem to correspond to the
typical solar semi-open quite extended magnetic configurations called helmet
streamers.} Aims {We aim to find direct observational evidence for the
postulated, solar-like, coronal topologies.} Methods {We performed
seven-consecutive-day VLBI observations at 8.4 GHz using an array consisting of
the VLBA and the 100-m Effelsberg telescope.} Results {Two distintive
structures appear in the radio images here presented. They happen to be
associated with the primary and secondary stars of the V773 Tau A system. In
one image (Fig.2-B) the two features are extended up to 18 R each and are
nearly parallel revealing the presence of two interacting helmet streamers. One
image (Fig.2-E) taken a few hours after a flare monitored by the 100-m
Effelsberg telescope shows one elongated fading structure substantially rotated
with respect to those seen in the B run. The same decay scenario is seen in
Fig.2-G for the helmet streamer associated with the other star.} Conclusions
{This is the very first direct evidence revealing that even if the flare origin
is magnetic reconnection due to interbinary collision, both stars independently
emit in the radio range with structures of their own. These structures are
helmet streamers, observed for the first time in stars other than the Sun.}Comment: 7 pages, 3 figures, A&A in pres
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
The Helium abundance and Delta Y / Delta Z in Lower Main Sequence stars
We use nearby K dwarf stars to measure the helium-to-metal enrichment ratio,
a diagnostic of the chemical history of the Solar Neighbourhood. Our sample of
K dwarfs has homogeneously determined effective temperatures, bolometric
luminosities and metallicities, allowing us to fit each star to the appropriate
stellar isochrone and determine its helium content indirectly. We use a newly
computed set of Padova isochrones which cover a wide range of helium and metal
content. Our theoretical isochrones have been checked against a congruous set
of main sequence binaries with accurately measured masses, to discuss and
validate their range of applicability. We find that the stellar masses deduced
from the isochrones are usually in excellent agreement with empirical
measurements. Good agreement is also found with empirical mass-luminosity
relations. Despite fitting the masses of the stars very well, we find that
anomalously low helium content (lower than primordial helium) is required to
fit the luminosities and temperatures of the metal poor K dwarfs, while more
conventional values of the helium content are derived for the stars around
solar metallicity. We have investigated the effect of diffusion in stellar
models and LTE assumption in deriving metallicities. Neither of these is able
to resolve the low helium problem alone and only marginally if the cumulated
effects are included, unless we assume a mixing-length which is strongly
decreasing with metallicity. Further work in stellar models is urgently needed.
The helium-to-metal enrichment ratio is found to be Delta Y / Delta Z = 2.1 +/-
0.9 around and above solar metallicity, consistent with previous studies,
whereas open problems still remain at the lowest metallicities. Finally, we
determine the helium content for a set of planetary host stars.Comment: 29 pages, 13 figures, replaced to match published version in MNRA
Access to highly active antiretroviral therapy for injection drug users: adherence, resistance, and death
Stressful life events are associated with insulin resistance among Chinese immigrant women in the United States
Background: Chinese immigrants experience increased chronic disease risk following migration to the US. Although the impact of lifestyle changes (e.g., diet) on disease risk has been extensively studied, associations of psychosocial stress and disease risk have attracted less attention. Thus, the objective of the present study was to examine associations between stress and insulin resistance in foreign-born Chinese American women.
Methods: From October, 2005 to April, 2008, 423 women recruited from southeastern Pennsylvania completed questionnaires reporting stressful life events. Blood samples were analyzed for fasting insulin and fasting glucose levels, which were used to estimate insulin resistance according to the homeostasis model assessment (HOMAIR).
Results: In logistic regression analyses, a greater number of negative life events were associated with insulin resistance (OR = 1.17, 95% CI = 1.02–1.34), controlling for age, level of acculturation, marital status, body mass index, and waist circumference. Similarly, greater negative life event impact ratings were also associated with insulin resistance (OR = 1.08, 95% CI = 1.01–1.16) controlling for relevant covariates.
Conclusions: This is one of the first studies to examine the associations between psychosocial stress and insulin resistance in Chinese immigrant women. These findings contribute to a growing body of literature on stress and diabetes risk in an immigrant population
Whole-blood tissue factor procoagulant activity is elevated in type 1 diabetes effects of hyperglycemia and hyperinsulinemia
OBJECTIVE - To determine tissue factor procoagulant activity (TF-PCA) in patients with type 1 diabetes and to examine effects of hyperglycemia and hyperglycemia plus hyperinsulinemia on TF-PCA. RESEARCH DESIGN AND METHODS - We have determined circulating TF-PCA and other coagulation factors under basal (hyperglycemic) conditions, after acute correction of hyperglycemia, in response to 24 h of selective hyperglycemia, and in response to 24 h of hyperglycemia plus hyperinsulinemia in nine type 1 diabetic patients and in seven nondiabetic control subjects. RESULTS - As shown previously in patients with type 2 diabetes, basal TF-PCA and plasma coagulation factor VIIa (FVIIa) were higher in patients with type 1 diabetes than in nondiabetic control subjects. However, in contrast with type 2 diabetes, normalizing glucose did not decrease the elevated TF-PCA levels, and raising glucose or glucose plus insulin levels did not increase TF-PCA. CONCLUSIONS - Patients with type 1 diabetes have elevated circulating TF-PCA and FVIIa levels and are in a procoagulant state that may predispose them to acute cardiovascular events. The mechanisms regulating TF-PCA in patients with type 1 and type 2 diabetes are different and should be further explored
High- or Low-Carbohydrate Diets: Which Is Better for Weight Loss, Insulin Resistance, and Fatty Livers?
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