244 research outputs found
FUV and X-ray irradiated protoplanetary disks: a grid of models I. The disk structure
Context. Planets are thought to eventually form from the mostly gaseous (~99%
of the mass) disks around young stars. The density structure and chemical
composition of protoplanetary disks are affected by the incident radiation
field at optical, FUV, and X-ray wavelengths, as well as by the dust
properties.
Aims. The effect of FUV and X-rays on the disk structure and the gas chemical
composition are investigated. This work forms the basis of a second paper,
which discusses the impact on diagnostic lines of, e.g., C+, O, H2O, and Ne+
observed with facilities such as Spitzer and Herschel.
Methods. A grid of 240 models is computed in which the X-ray and FUV
luminosity, minimum grain size, dust size distribution, and surface density
distribution are varied in a systematic way. The hydrostatic structure and the
thermo-chemical structure are calculated using ProDiMo.
Results. The abundance structure of neutral oxygen is stable to changes in
the X-ray and FUV luminosity, and the emission lines will thus be useful
tracers of the disk mass and temperature. The C+ abundance distribution is
sensitive to both X-rays and FUV. The radial column density profile shows two
peaks, one at the inner rim and a second one at a radius r=5-10 AU. Ne+ and
other heavy elements have a very strong response to X-rays, and the column
density in the inner disk increases by two orders of magnitude from the lowest
(LX = 1e29 erg/s) to the highest considered X-ray flux (LX = 1e32 erg/s). FUV
confines the Ne+ ionized region to areas closer to the star at low X-ray
luminosities (LX = 1e29 erg/s). H2O abundances are enhanced by X-rays due to
higher temperatures in the inner disk and higher ionization fractions in the
outer disk. The line fluxes and profiles are affected by the effects on these
species, thus providing diagnostic value in the study of FUV and X-ray
irradiated disks around T Tauri stars. (abridged)Comment: 47 pages, accepted by Astronomy and Astrophysics, a high resolution
version of the paper is located at
http://www.astro.rug.nl/~meijerink/disk_paperI_xrays.pd
Uncertainties in water chemistry in disks: An application to TW Hya
Context. This paper discusses the sensitivity of water lines to chemical
processes and radiative transfer for the protoplanetary disk around TW Hya. The
study focuses on the Herschel spectral range in the context of new line
detections with the PACS instrument from the Gas in Protoplanetary Systems
project (GASPS). Aims. The paper presents an overview of the chemistry in the
main water reservoirs in the disk around TW Hya. It discusses the limitations
in the interpretation of observed water line fluxes. Methods. ... (abbreviated)
Results. We report new line detections of p-H2O (3_22-2_11) at 89.99 micron and
CO J=18-17 at 144.78 micron for the disk around TW Hya. Disk modeling shows
that the far-IR fine structure lines ([OI], [CII]) and molecular submm lines
are very robust to uncertainties in the chemistry, while the water line fluxes
can change by factors of a few. The water lines are optically thick,
sub-thermally excited and can couple to the background continuum radiation
field. The low-excitation water lines are also sensitive to uncertainties in
the collision rates, e.g. with neutral hydrogen. The gas temperature plays an
important role for the [OI] fine structure line fluxes, the water line fluxes
originating from the inner disk as well as the high excitation CO, CH+ and OH
lines. Conclusions. Due to their sensitivity on chemical input data and
radiative transfer, water lines have to be used cautiously for understanding
details of the disk structure. Water lines covering a wide range of excitation
energies provide access to the various gas phase water reservoirs (inside and
outside the snow line) in protoplanetary disks and thus provide important
information on where gas-phase water is potentially located. Experimental
and/or theoretical collision rates for H2O with atomic hydrogen are needed to
diminish uncertainties from water line radiative transfer.Comment: accepted for publication in A&
[OI] disk emission in the Taurus star forming region
The structure of protoplanetary disks is thought to be linked to the
temperature and chemistry of their dust and gas. Whether the disk is flat or
flaring depends on the amount of radiation that it absorbs at a given radius,
and on the efficiency with which this is converted into thermal energy. The
understanding of these heating and cooling processes is crucial to provide a
reliable disk structure for the interpretation of dust continuum emission and
gas line fluxes. Especially in the upper layers of the disk, where gas and dust
are thermally decoupled, the infrared line emission is strictly related to the
gas heating/cooling processes. We aim to study the thermal properties of the
disk in the oxygen line emission region, and to investigate the relative
importance of X-ray (1-120 Angstrom) and far-UV radiation (FUV, 912-2070
Angstrom) for the heating balance there. We use [OI] 63 micron line fluxes
observed in a sample of protoplanetary disks of the Taurus/Auriga star forming
region and compare it to the model predictions presented in our previous work.
The data were obtained with the PACS instrument on board the Herschel Space
Observatory as part of the Herschel Open Time Key Program GASPS (GAS in
Protoplanetary diskS), published in Howard et al. (2013). Our theoretical grid
of disk models can reproduce the [OI] absolute fluxes and predict a correlation
between [OI] and the sum Lx+Lfuv. The data show no correlation between the [OI]
line flux and the X-ray luminosity, the FUV luminosity or their sum. The data
show that the FUV or X-ray radiation has no notable impact on the region where
the [OI] line is formed. This is in contrast with what is predicted from our
models. Possible explanations are that the disks in Taurus are less flaring
than the hydrostatic models predict, and/or that other disk structure aspects
that were left unchanged in our models are important. ..abridged..Comment: 9 pages, accepted for publication in A&
A systematic study of \ce{CO2} planetary atmospheres and their link to the stellar environment
The Milky Way Galaxy is literally teeming with exoplanets; thousands of
planets have been discovered, with thousands more planet candidates identified.
Terrestrial-like planets are quite common around other stars, and are expected
to be detected in large numbers in the future. Such planets are the primary
targets in the search for potentially habitable conditions outside the solar
system.
Determining the atmospheric composition of exoplanets is mandatory to
understand their origin and evolution, as atmospheric processes play crucial
roles in many aspects of planetary architecture. In this work we construct and
exploit a 1D radiative transfer model based on the discrete-ordinates method in
plane-parallel geometry. Radiative results are linked to a convective flux that
redistributes energy at any altitude producing atmospheric profiles in
radiative-convective equilibrium. The model has been applied to a large number
(6250) of closely dry synthetic \ce{CO2} atmospheres, and the resulting
pressure and thermal profiles have been interpreted in terms of parameter
variability. Although less accurate than 3D general circulation models, not
properly accounting for e.g., clouds and atmospheric and ocean dynamics, 1D
descriptions are computationally inexpensive and retain significant value by
allowing multidimensional parameter sweeps with relative ease.Comment: 12 pages, 9 figures, accepted for publication in MNRA
Environmental monitoring programme in the cell therapy facility of a research centre: preliminary investigation
Introduction. Recent discoveries in cell therapy research present new opportunities for cellular products to be used to treat severe, and as yet incurable, diseases. It is therefore essential to implement a quality control programme in order to ensure that safe cells and tissues are provided.
Methods. In a preliminary phase of the setting up of a the cell factory, monitoring was carried out monthly over a 6-month period in one out of three cell therapy laboratories and filter rooms in order to evaluate the microbial contamination of air and surfaces and the presence of airborne particulates.
Results. The mean total bacterial and fungal loads measured in the air in the centre of the filter room were 20.7 ñ 28.9 colonyforming units (cfu)/m3 and 9.2 ñ 15.4 cfu/m3, respectively, and
5.2 ñ 4.1 cfu/m3 and 6.8 ñ 13.4 cfu/m3, respectively, in the laboratory.
The mean fungal load values recorded on the surfaces sampled in the laboratory were in 6 out of 18 cases higher than the reference values (5 cfu/plate). As to the results of particulate
monitoring, with regard to the 0.5 ?m particles, about 83% of the samples revealed values below the limit of 350.000 particles per cubic metre.
Conclusions. In this set-up phase, monitoring was able to pick out structural and organisational flaws acceptable in a laboratory compliant with Good Manufacturing Practices class C (Annex 1), but not in a class B facility. Thanks to this preliminary monitoring phase, and by correcting these flaws, the clean room facility could achieve compliance to class B
Prognostic value of pd-l1, pd-1 and cd8a in canine diffuse large b-cell lymphoma detected by rnascope
Immune checkpoints are a set of molecules dysregulated in several human and canine cancers and aberrations of the PD-1/PD-L1 axis are often correlated with a worse prognosis. To gain an insight into the role of immune checkpoints in canine diffuse large B-cell lymphoma (cDLBCL), we investigated PD-L1, PD-1 and CD8A expression by RNAscope. Results were correlated with several clinico-pathological features, including treatment, Ki67 index and outcome. A total of 33 dogs treated with chemotherapy (n = 12) or chemoimmunotherapy with APAVAC (n = 21) were included. PD-L1 signal was diffusely distributed among neoplastic cells, whereas PD-1 and CD8A were localized in tumor infiltrating lymphocytes. However, PD-1 mRNA was also retrieved in tumor cells. An association between PD-L1 and PD-1 scores was identified and a higher risk of relapse and lymphoma-related death was found in dogs treated with chemotherapy alone and dogs with higher PD-L1 and PD-1 scores. The correlation between PD-L1 and PD-1 is in line with the mechanism of immune checkpoints in cancers, where neoplastic cells overexpress PD-L1 that, in turn, binds PD-1 receptors in activated TIL. We also found that Ki67 index was significantly increased in dogs with the highest PD-L1 and PD-1 scores, indirectly suggesting a role in promoting tumor proliferation. Finally, even if the biological consequence of PD-1+ tumor cells is unknown, our findings suggest that PD-1 intrinsic expression in cDLBCL might contribute to tumor growth escaping adaptive immunity
Dietary assessment of British police force employees: A description of diet record coding procedures and cross-sectional evaluation of dietary energy intake reporting (The Airwave Health Monitoring Study)
Objectives: Dietary intake is a key aspect of occupational health. To capture the characteristics of dietary behaviour that is affected by occupational environment that may affect disease risk, a collection of prospective multiday dietary records is required. The aims of this paper are to: (1) collect multiday dietary data in the Airwave Health Monitoring Study, (2) describe the di etary coding procedures applied and (3) investigate the plausibility of dietary reporting in this occupational cohort. Design: A dietary coding protocol for this large-scale study was developed to minimise coding error rate. Participants (n 4412) who completed 7-day food records were included for cross-sectional analyses. Energy intake (EI) misreporting was estimated using the Goldberg method. Multivariate logistic regression models were applied to determine participant characteristics associated with EI misreporting. Setting: British police force employees enrolled (2007-2012) into the Airwave Health Monitoring Study. Results: The mean code error rate per food diary was 3.7% (SD 3.2%). The strongest predictors of EI under-reporting were body mass index (BMI) and physical activity. Compared with participants with BMI 30 kg/m2 had increased odds of being classified as under-reporting EI (men OR 5.20 95% CI 3.92 to 6.89; women OR 2.66 95% CI 1.85 to 3.83). Men and women in the highest physical activity category compared with the lowest were also more likely to be classified as underreporting (men OR 3.33 95% CI 2.46 to 4.50; women OR 4.34 95% CI 2.91 to 6.55). Conclusions: A reproducible dietary record coding procedure has been developed to minimise coding error in complex 7-day diet diaries. The prevalence of EI under-reporting is comparable with existing national UK cohorts and, in agreement with previous studies, classification of under-reporting was biased towards specific subgroups of participants
Thermochemical modelling of brown dwarf discs
RCH acknowledges funding by the Austrian Science Fund (FWF): project number P24790.The physical properties of brown dwarf discs, in terms of their shapes and sizes, are still largely unexplored by observations. ALMA has by far the best capabilities to observe these discs in sub-mm CO lines and dust continuum, while also spatially resolving some discs. To what extent brown dwarf discs are similar to scaled-down T Tauri discs is currently unknown, and this work is a step towards establishing a relationship through the eventual modelling of future observations. We use observations of the brown dwarf disc Ï Oph 102 to infer a fiducial model around which we build a small grid of brown dwarf disc models, in order to model the CO, HCN, and HCO+ line fluxes and the chemistry which drives their abundances. These are the first brown dwarf models to be published which relate detailed, 2D radiation thermochemical disc models to observational data. We predict that moderately extended ALMA antenna configurations will spatially resolve CO line emission around brown dwarf discs, and that HCN and HCO+ will be detectable in integrated flux, following our conclusion that the flux ratios of these molecules to CO emission are comparable to that of T Tauri discs. These molecules have not yet been observed in sub-mm wavelengths in a brown dwarf disc, yet they are crucial tracers of the warm surface-layer gas and of ionization in the outer parts of the disc. We present the prediction that if the physical and chemical processes in brown dwarf discs are similar to those that occur in T Tauri discs-as our models suggest-then the same diagnostics that are used for T Tauri discs can be used for brown dwarf discs (such as HCN and HCO+ lines that have not yet been observed in the sub-mm), and that these lines should be observable with ALMA. Through future observations, either confirmation (or refutation) of these ideas about brown dwarf disc chemistry will have strong implications for our understanding of disc chemistry, structure, and subsequent planet formation in brown dwarf discs.Publisher PDFPeer reviewe
The Italian-Canine Cancer (ICC) Biobank: our 10-year challenge
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