681 research outputs found
Lutropin alpha, recombinant human luteinizing hormone, for the stimulation of follicular development in profoundly LH-deficient hypogonadotropic hypogonadal women: a review
Hypogonadotropic hypogonadism is defined as a medical condition with low or undetectable gonadotropin secretion, associated with a complete arrest of follicular growth and very low estradiol. The main cause can be traced back to an irregular or absent hypothalamic GnRH secretion, whereas only a minority suffers from a pituitary disorder. The choice of treatment to reverse this situation is a pulsatile GnRH application or a direct ovarian stimulation using gonadotropin injections. The goal is to achieve a proper ovarian function in these cases for a short time to allow ovulation and chance of pregnancy. Since the pulsatile GnRH treatment lost its former importance, several gonadotropins are in use to stimulate follicular growth, such as urine-derived human menopausal gonadotropin, highly purified follicle stimulating hormone (FSH) or recombinant FSH, all with different success. The introduction of recombinant luteinizing hormone (LH) and FSH provided an opportunity to investigate the distinct influences of LH and FSH alone and in combination on follicular growth in monofollicular ovulation induction cycles, and additionally on oocyte maturation, fertilization competence of the oocyte and embryo quality in downregulated IVF patients. Whereas FSH was known to be indispensable for normal follicular growth, the role of LH remained questionable. Downregulated IVF patients with this short-term gonadotropin depletion displayed no advance in stimulation success with the use of recombinant LH. Patients with hypogonadotropic hypogonadism undergoing monofollicular stimulation for ovulation induction showed clearly a specific role and need for both hormones in normal follicular growth. Therefore, a combined stimulation with FSH and LH seems to be the best treatment choice. In the first half of the stimulation cycle the FSH dosage should exceed that of LH by 2:1, with an inverse ratio for the second half
Kinematic and Thermal Structure at the onset of high-mass star formation
We want to understand the kinematic and thermal properties of young massive
gas clumps prior to and at the earliest evolutionary stages of high-mass star
formation. Do we find signatures of gravitational collapse? Do we find
temperature gradients in the vicinity or absence of infrared emission sources?
Do we find coherent velocity structures toward the center of the dense and cold
gas clumps? To determine kinematics and gas temperatures, we used ammonia,
because it is known to be a good tracer and thermometer of dense gas. We
observed the NH(1,1) and (2,2) lines within seven very young high-mass
star-forming regions with the VLA and the Effelsberg 100m telescope. This
allows us to study velocity structures, linewidths, and gas temperatures at
high spatial resolution of 3-5, corresponding to 0.05 pc. We find on
average cold gas clumps with temperatures in the range between 10 K and 30 K.
The observations do not reveal a clear correlation between infrared emission
peaks and ammonia temperature peaks. We report an upper limit for the linewidth
of 1.3 km s, at the spectral resolution limit of our VLA
observation. This indicates a relatively low level of turbulence on the scale
of the observations. Velocity gradients are present in almost all regions with
typical velocity differences of 1 to 2 km s and gradients of 5 to 10 km
s pc. These velocity gradients are smooth in most cases, but
there is one exceptional source (ISOSS23053), for which we find several
velocity components with a steep velocity gradient toward the clump centers
that is larger than 30 km s pc. This steep velocity gradient is
consistent with recent models of cloud collapse. Furthermore, we report a
spatial correlation of ammonia and cold dust, but we also find decreasing
ammonia emission close to infrared emission sources.Comment: 20 pages, 10 figure
The Earliest Phases of Star formation (EPoS): Temperature, density, and kinematic structure of the star-forming core CB 17
Context: The initial conditions for the gravitational collapse of molecular
cloud cores and the subsequent birth of stars are still not well constrained.
The characteristic cold temperatures (about 10 K) in such regions require
observations at sub-millimetre and longer wavelengths. The Herschel Space
Observatory and complementary ground-based observations presented in this paper
have the unprecedented potential to reveal the structure and kinematics of a
prototypical core region at the onset of stellar birth.
Aims: This paper aims to determine the density, temperature, and velocity
structure of the star-forming Bok globule CB 17. This isolated region is known
to host (at least) two sources at different evolutionary stages: a dense core,
SMM1, and a Class I protostar, IRS.
Methods: We modeled the cold dust emission maps from 100 micron to 1.2 mm
with both a modified blackbody technique to determine the optical
depth-weighted line-of-sight temperature and column density and a ray-tracing
technique to determine the core temperature and volume density structure.
Furthermore, we analysed the kinematics of CB17 using the high-density gas
tracer N2H+.
Results: From the ray-tracing analysis, we find a temperature in the centre
of SMM1 of 10.6 K, a flat density profile with radius 9500 au, and a central
volume density of n(H) = 2.3x10^5 cm-3. The velocity structure of the N2H+
observations reveal global rotation with a velocity gradient of 4.3 km/s/pc.
Superposed on this rotation signature we find a more complex velocity field,
which may be indicative of differential motions within the dense core.
Conclusions: SMM is a core in an early evolutionary stage at the verge of
being bound, but the question of whether it is a starless or a protostellar
core remains unanswered.Comment: published in A&
Carbon in different phases ([CII], [CI], and CO) in infrared dark clouds: Cloud formation signatures and carbon gas fractions
Context: How do molecular clouds form out of the atomic phase? And what are
the relative fractions of carbon in the ionized, atomic and molecular phase?
These are questions at the heart of cloud and star formation. Methods: Using
multiple observatories from Herschel and SOFIA to APEX and the IRAM 30m
telescope, we mapped the ionized, atomic and molecular carbon ([CII]@1900GHz,
[CI]@492GHz and C18O(2-1)@220GHz) at high spatial resolution (12"-25") in four
young massive infrared dark clouds (IRDCs). Results: The three carbon phases
were successfully mapped in all four regions, only in one source the [CII] line
remained a non-detection. Both the molecular and atomic phases trace the dense
structures well, with [CI] also tracing material at lower column densities.
[CII] exhibits diverse morphologies in our sample, from compact to diffuse
structures probing the cloud environment. In at least two out of the four
regions, we find kinematic signatures strongly indicating that the dense gas
filaments have formed out of a dynamically active and turbulent
atomic/molecular cloud, potentially from converging gas flows. The
atomic-to-molecular carbon gas mass ratios are low between 7% and 12% with the
lowest values found toward the most quiescent region. In the three regions
where [CII] is detected, its mass is always higher by a factor of a few than
that of the atomic carbon. The ionized carbon emission depends as well on the
radiation field, however, we also find strong [CII] emission in a region
without significant external sources, indicating that other processes, e.g.,
energetic gas flows can contribute to the [CII] excitation as well.Comment: 15 pages, 18 figures, accepted by Astronomy & Astrophysics, a higher
resolution version can be found at
http://www.mpia.de/homes/beuther/papers.htm
Kinematic structure of massive star-forming regions - I. Accretion along filaments
The mid- and far-infrared view on high-mass star formation, in particular
with the results from the Herschel space observatory, has shed light on many
aspects of massive star formation. However, these continuum studies lack
kinematic information.
We study the kinematics of the molecular gas in high-mass star-forming
regions.
We complemented the PACS and SPIRE far-infrared data of 16 high-mass
star-forming regions from the Herschel key project EPoS with N2H+ molecular
line data from the MOPRA and Nobeyama 45m telescope. Using the full N2H+
hyperfine structure, we produced column density, velocity, and linewidth maps.
These were correlated with PACS 70micron images and PACS point sources. In
addition, we searched for velocity gradients.
For several regions, the data suggest that the linewidth on the scale of
clumps is dominated by outflows or unresolved velocity gradients. IRDC18454 and
G11.11 show two velocity components along several lines of sight. We find that
all regions with a diameter larger than 1pc show either velocity gradients or
fragment into independent structures with distinct velocities. The velocity
profiles of three regions with a smooth gradient are consistent with gas flows
along the filament, suggesting accretion flows onto the densest regions.
We show that the kinematics of several regions have a significant and complex
velocity structure. For three filaments, we suggest that gas flows toward the
more massive clumps are present.Comment: accepted by A&
Fragmentation and dynamical collapse of the starless high-mass star-forming region IRDC18310-4
Aims: We study the fragmentation and dynamical properties of a massive
starless gas clump at the onset of high-mass star formation. Methods: Based on
Herschel continuum data we identify a massive gas clump that remains
far-infrared dark up to 100mum wavelengths. The fragmentation and dynamical
properties are investigated by means of Plateau de Bure Interferometer and
Nobeyama 45m single-dish spectral line and continuum observations. Results: The
massive gas reservoir fragments at spatial scales of ~18000AU in four cores.
Comparing the spatial extent of this high-mass region with intermediate- to
low-mass starless cores from the literature, we find that linear sizes do not
vary significantly over the whole mass regime. However, the high-mass regions
squeeze much more gas into these similar volumes and hence have orders of
magnitude larger densities. The fragmentation properties of the presented
low-to high-mass regions are consistent with gravitational instable Jeans
fragmentation. Furthermore, we find multiple velocity components associated
with the resolved cores. Recent radiative transfer hydrodynamic simulations of
the dynamic collapse of massive gas clumps also result in multiple velocity
components along the line of sight because of the clumpy structure of the
regions. This result is supported by a ratio between viral and total gas mass
for the whole region <1. Conclusions: This apparently still starless high-mass
gas clump exhibits clear signatures of early fragmentation and dynamic collapse
prior to the formation of an embedded heating source. A comparison with regions
of lower mass reveals that the linear size of star-forming regions does not
necessarily have to vary much for different masses, however, the mass
reservoirs and gas densities are orders of magnitude enhanced for high-mass
regions compared to their lower-mass siblings.Comment: 11 pages, 10 figures, accepted to Astronomy and Astrophysics,
high-resolution version with all figures included can be found at
http://www.mpia.de/homes/beuther/papers.htm
Gas-phase CO depletion and N2H+ abundances in starless cores
Seven isolated, nearby low-mass starless molecular cloud cores have been
observed as part of the Herschel key program Earliest Phases of Star formation
(EPoS). By applying a ray-tracing technique to the obtained continuum emission
and complementary (sub)mm emission maps, we derive the physical structure
(density, dust temperature) of these cloud cores. We present observations of
the 12CO, 13CO, and C18O (2-1) and N2H+ (1-0) transitions towards the same
cores. Based on the density and temperature profiles, we apply time-dependent
chemical and line-radiative transfer modeling and compare the modeled to the
observed molecular emission profiles. CO is frozen onto the grains in the
center of all cores in our sample. The level of CO depletion increases with
hydrogen density and ranges from 46% up to more than 95% in the core centers in
the core centers in the three cores with the highest hydrogen density. The
average hydrogen density at which 50% of CO is frozen onto the grains is
1.1+-0.4 10^5 cm^-3. At about this density, the cores typically have the
highest relative abundance of N2H+. The cores with higher central densities
show depletion of N2H+ at levels of 13% to 55%. The chemical ages for the
individual species are on average 2+-1 10^5 yr for 13CO, 6+-3 10^4 yr for C18O,
and 9+-2 10^4 yr for N2H+. Chemical modeling indirectly suggests that the gas
and dust temperatures decouple in the envelopes and that the dust grains are
not yet significantly coagulated. We observationally confirm chemical models of
CO-freezeout and nitrogen chemistry. We find clear correlations between the
hydrogen density and CO depletion and the emergence of N2H+. The chemical ages
indicate a core lifetime of less than 1 Myr.Comment: 24 pages, 25 figures, Accepted for publication in Astronomy and
Astrophysic
Plasma arginine vasopressin concentrations in epileptics under monotherapy
Plasma arginine vasopressin concentrations were determined by radio-immunoassay in 112 adult epileptics who were taking carbamazepine, phenytoin, primidone, or sodium valproate in long-term monotherapy, and in 19 controls. No significant difference was found between the groups, but some epileptics taking carbamazepine and primidone showed low values. Serum
concentrations of carbamazepine did not correlate with the concentrations of plasma arginine vasopressin.
In conclusion, there was no evidence of a stimulating
effect of chronic carbamazepine medication or a special inhibiting effect of phenytoin on the release of vasopressin arginine from the posterior pituitary
The structured environments of embedded star-forming cores. PACS and SPIRE mapping of the enigmatic outflow source UYSO 1
The intermediate-mass star-forming core UYSO 1 has previously been found to
exhibit intriguing features. While deeply embedded and previously only
identified by means of its (sub-)millimeter emission, it drives two powerful,
dynamically young, molecular outflows. Although the process of star formation
has obviously started, the chemical composition is still pristine. We present
Herschel PACS and SPIRE continuum data of this presumably very young region.
The now complete coverage of the spectral energy peak allows us to precisely
constrain the elevated temperature of 26 - 28 K for the main bulge of gas
associated with UYSO1, which is located at the interface between the hot HII
region Sh 2-297 and the cold dark nebula LDN 1657A. Furthermore, the data
identify cooler compact far-infrared sources of just a few solar masses, hidden
in this neighbouring dark cloud.Comment: accepted contribution for the forthcoming Herschel Special Issue of
A&A, 5 pages (will appear as 4-page letter in the journal), 6 figure file
Do Arsenic Interstitials Really Exist in As-Rich GaAs?
To investigate the lattice distortion caused by point defects in As-rich GaAs, we make use of a self-consistent-charge density-functional based tight-binding method. Both relevant defects, the As antisite and the As interstitial, cause significant lattice distortion. In contrast to As interstitials, isolated As antisites lead to lattice strain as well as displacement of nearest neighbor As lattice atoms into the ⟨110⟩ channels, in excellent agreement with experiments. Therefore, our result gives powerful evidence for As antisites being the dominating defect in as-grown As-rich GaAs.Peer reviewe
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