547 research outputs found
Gas and Dust Emission at the Outer Edge of Protoplanetary Disks
We investigate the apparent discrepancy between gas and dust outer radii
derived from millimeter observations of protoplanetary disks. Using 230 and 345
GHz continuum and CO J=3-2 data from the Submillimeter Array for four nearby
disk systems (HD 163296, TW Hydrae, GM Aurigae, and MWC 480), we examine models
of circumstellar disk structure and the effects of their treatment of the outer
disk edge. We show that for these disks, models described by power laws in
surface density and temperature that are truncated at an outer radius are
incapable of reproducing both the gas and dust emission simultaneously: the
outer radius derived from the dust continuum emission is always significantly
smaller than the extent of the molecular gas disk traced by CO emission.
However, a simple model motivated by similarity solutions of the time evolution
of accretion disks that includes a tapered exponential edge in the surface
density distribution (and the same number of free parameters) does much better
at reproducing both the gas and dust emission. While this analysis does not
rule out the disparate radii implied by the truncated power-law models, a
realistic alternative disk model, grounded in the physics of accretion,
provides a consistent picture for the extent of both the gas and dust.Comment: 9 pages, 2 figures, accepted for publication in Ap
Leisure of family as a pedagogical problem
The pedagogical value of family leisure forms is that they actively involve and intensively use various communication mechanisms: family - children, family - family, children - children, children - teenagers - adults. The simultaneity of these contacts gives the family leisure emotional appeal, sincerity, warmth. Intra-family leisure relationships are already in themselves rehabilitative function, actively influencing the creation of a favorable psychological climate in the family.Педагогическая ценность семейных досуговых форм состоит в том, что в них активно включены и интенсивно задействованы различные механизмы общения: семья - дети, семья - семья, дети - дети, дети - подростки - взрослые. Одновременность этих контактов придает семейному досугу эмоциональную привлекательность, душевность, теплоту. Внутрисемейные досуговые отношения уже сами по себе несут реабилитирующую функцию, активно воздействуют на создание благоприятного психологического климата в семье
Stringent Limits on the Polarized Submillimeter Emission from Protoplanetary Disks
We present arcsecond-resolution Submillimeter Array (SMA) polarimetric
observations of the 880 um continuum emission from the protoplanetary disks
around two nearby stars, HD 163296 and TW Hydrae. Although previous
observations and theoretical work have suggested that a 2-3% polarization
fraction should be common for the millimeter continuum emission from such
disks, we detect no polarized continuum emission above a 3-sigma upper limit of
7 mJy in each arcsecond-scale beam, or <1% in integrated continuum emission. We
compare the SMA upper limits with the predictions from the exploratory Cho &
Lazarian (2007) model of polarized emission from T Tauri disks threaded by
toroidal magnetic fields, and rule out their fiducial model at the ~10-sigma
level. We explore some potential causes for this discrepancy, focusing on model
parameters that describe the shape, magnetic field alignment, and size
distribution of grains in the disk. We also investigate related effects like
the magnetic field strength and geometry, scattering off of large grains, and
the efficiency of grain alignment, including recent advances in grain alignment
theory, which are not considered in the fiducial model. We discuss the impact
each parameter would have on the data and determine that the suppression of
polarized emission plausibly arises from rounding of large grains, reduced
efficiency of grain alignment with the magnetic field, and/or some degree of
magnetic field tangling (perhaps due to turbulence). A poloidal magnetic field
geometry could also reduce the polarization signal, particularly for a face-on
viewing geometry like the TW Hya disk. The data provided here offer the most
stringent limits to date on the polarized millimeter-wavelength emission from
disks around young stars.Comment: 15 pages, 6 figures, accepted for publication in Ap
New highlights on stroma–epithelial interactions in breast cancer
Although the stroma in which carcinomas arise has been previously regarded as a bystander to the clonal expansion and acquisition of malignant characteristics of tumor cells, it is now generally acknowledged that stromal changes are required for the establishment of cancer. In the present article, we discuss three recent publications that highlight the complex role the stroma has during the development of cancer and the potential for targeting the stroma by therapeutic approaches
Vagus nerve stimulation for depression: efficacy and safety in a European study
Background Vagus nerve stimulation (VNS) therapy is associated with a decrease in seizure frequency in partial-onset seizure patients. Initial trials suggest that it may be an effective treatment, with few side-effects, for intractable depression. Method An open, uncontrolled European multi-centre study (D03) of VNS therapy was conducted, in addition to stable pharmacotherapy, in 74 patients with treatment-resistant depression (TRD). Treatment remained unchanged for the first 3 months; in the subsequent 9 months, medications and VNS dosing parameters were altered as indicated clinically. Results The baseline 28-item Hamilton Depression Rating Scale (HAMD-28) score averaged 34. After 3 months of VNS, response rates (50% reduction in baseline scores) reached 37% and remission rates (HAMD-28 score <10) 17%. Response rates increased to 53% after 1 year of VNS, and remission rates reached 33%. Response was defined as sustained if no relapse occurred during the first year of VNS after response onset; 44% of patients met these criteria. Median time to response was 9 months. Most frequent side-effects were voice alteration (63% at 3 months of stimulation) and coughing (23%). Conclusions VNS therapy was effective in reducing severity of depression; efficacy increased over time. Efficacy ratings were in the same range as those previously reported from a USA study using a similar protocol; at 12 months, reduction of symptom severity was significantly higher in the European sample. This might be explained by a small but significant difference in the baseline HAMD-28 score and the lower number of treatments in the current episode in the European stud
Comprehensive Gene-Expression Survey Identifies Wif1 as a Modulator of Cardiomyocyte Differentiation
During chicken cardiac development the proepicardium (PE) forms the epicardium (Epi), which contributes to several non-myocardial lineages within the heart. In contrast to Epi-explant cultures, PE explants can differentiate into a cardiomyocyte phenotype. By temporal microarray expression profiles of PE-explant cultures and maturing Epi cells, we identified genes specifically associated with differentiation towards either of these lineages and genes that are associated with the Epi-lineage restriction. We found a central role for Wnt signaling in the determination of the different cell lineages. Immunofluorescent staining after recombinant-protein incubation in PE-explant cultures indicated that the early upregulated Wnt inhibitory factor-1 (Wif1), stimulates cardiomyocyte differentiation in a similar manner as Wnt stimulation. Concordingly, in the mouse pluripotent embryogenic carcinoma cell line p19cl6, early and late Wif1 exposure enhances and attenuates differentiation, respectively. In ovo exposure of the HH12 chicken embryonic heart to Wif1 increases the Tbx18-positive cardiac progenitor pool. These data indicate that Wif1 enhances cardiomyogenesis
Amplification efficiency: linking baseline and bias in the analysis of quantitative PCR data
Despite the central role of quantitative PCR (qPCR) in the quantification of mRNA transcripts, most analyses of qPCR data are still delegated to the software that comes with the qPCR apparatus. This is especially true for the handling of the fluorescence baseline. This article shows that baseline estimation errors are directly reflected in the observed PCR efficiency values and are thus propagated exponentially in the estimated starting concentrations as well as ‘fold-difference’ results. Because of the unknown origin and kinetics of the baseline fluorescence, the fluorescence values monitored in the initial cycles of the PCR reaction cannot be used to estimate a useful baseline value. An algorithm that estimates the baseline by reconstructing the log-linear phase downward from the early plateau phase of the PCR reaction was developed and shown to lead to very reproducible PCR efficiency values. PCR efficiency values were determined per sample by fitting a regression line to a subset of data points in the log-linear phase. The variability, as well as the bias, in qPCR results was significantly reduced when the mean of these PCR efficiencies per amplicon was used in the calculation of an estimate of the starting concentration per sample
Photon vs. proton radiochemotherapy: Effects on brain tissue volume and perfusion
Neuro Imaging Researc
Field comparison of two novel open-path instruments that measure dry deposition and emission of ammonia using flux-gradient and eddy covariance methods
Dry deposition of ammonia (NH3) is the largest
contributor to the nitrogen deposition from the atmosphere to soil and
vegetation in the Netherlands, causing eutrophication and loss of
biodiversity; however, data sets of NH3 fluxes are sparse and in general
have monthly resolution at best. An important reason for this is that
measurement of the NH3 flux under dry conditions is notoriously
difficult. There is no technique that can be considered as the gold
standard for these measurements, which complicates the testing of new
techniques. Here, we present the results of an intercomparison of two novel
measurement set-ups aimed at measuring dry deposition of NH3 at
half hourly resolution. Over a 5-week period, we operated two novel optical
open-path techniques side by side at the Ruisdael station in Cabauw, the
Netherlands: the RIVM-miniDOAS 2.2D using the aerodynamic gradient
technique, and the commercial Healthy Photon HT8700E using the eddy
covariance technique. These instruments are widely different in their
measurement principle and approach to derive deposition values from measured
concentrations; however, both techniques showed very similar results (r=0.87)
and small differences in cumulative fluxes (∼ 10 %) as long
as the upwind terrain was homogeneous and free of nearby obstacles. The
observed fluxes varied from ∼ −80 to ∼ +140 ng NH3 m−2 s−1. Both the absolute flux values and the temporal
patterns were highly similar, which substantiates that both instruments were
able to measure NH3 fluxes at high temporal resolution. However, for
wind directions with obstacles nearby, the correlations between the two
techniques were weaker. The uptime of the miniDOAS system reached 100 %
once operational, but regular intercalibration of the system was applied in
this campaign (35 % of the 7-week uptime). Conversely, the HT8700E did not
measure during and shortly after rain, and the coating of its mirrors
tended to degrade (21 % data loss during the 5-week uptime). In addition,
the NH3 concentrations measured by the HT8700E proved sensitive to air
temperature, causing substantial differences (range: −15 to +6 µg m−3) between the two systems. To conclude, the miniDOAS system appears
ready for long-term hands-off monitoring. The current HT8700E system, on the
other hand, had a limited stand-alone operational time under the prevailing
weather conditions. However, under relatively dry and low-dust conditions,
the system can provide sound results, opening good prospects for future
versions, also for monitoring applications. The new high temporal resolution
data from these instruments can facilitate the study of processes behind
NH3 dry deposition, allowing an improved understanding of these
processes and better parameterisation in chemical transport models.</p
The BMP Antagonist Follistatin-Like 1 Is Required for Skeletal and Lung Organogenesis
Follistatin-like 1 (Fstl1) is a secreted protein of the BMP inhibitor class. During development, expression of Fstl1 is already found in cleavage stage embryos and becomes gradually restricted to mesenchymal elements of most organs during subsequent development. Knock down experiments in chicken and zebrafish demonstrated a role as a BMP antagonist in early development. To investigate the role of Fstl1 during mouse development, a conditional Fstl1 KO allele as well as a Fstl1-GFP reporter mouse were created. KO mice die at birth from respiratory distress and show multiple defects in lung development. Also, skeletal development is affected. Endochondral bone development, limb patterning as well as patterning of the axial skeleton are perturbed in the absence of Fstl1. Taken together, these observations show that Fstl1 is a crucial regulator in BMP signalling during mouse development
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