scholarly journals The extraordinary composition of the blue comet C/2016 R2 (PanSTARRS)

2018 ◽  
Vol 619 ◽  
pp. A127 ◽  
Author(s):  
N. Biver ◽  
D. Bockelée-Morvan ◽  
G. Paubert ◽  
R. Moreno ◽  
J. Crovisier ◽  
...  
Keyword(s):  
Radio Telescope ◽  
Heliocentric Distance ◽  
Abundance Ratio ◽  
Visible Spectroscopy ◽  
Production Rates ◽  
Sulfur Species ◽  
Upper Limits ◽  
Multi Wavelength ◽  
Rare Group

We present a multi-wavelength study of comet C/2016 R2 (PanSTARRS). This comet was observed on 23 and 24 January 2018 with the IRAM 30 m telescope, and in January to March 2018 with the Nançay radio telescope. Visible spectroscopy was performed in December 2017 and February 2018 with small amateur telescopes. We report on measurements of CO, CH3OH, H2CO and HCN production rates, and on the determination of the N2/CO abundance ratio. Several other species, especially OH, were searched for but not detected. The inferred relative abundances, including upper limits for sulfur species, are compared to those measured in other comets at about the same heliocentric distance of ~2.8 AU. The coma composition of comet C/2016 R2 is very different from all other comets observed so far, being rich in N2 and CO and dust poor. This suggests that this comet might belong to a very rare group of comets formed beyond the N2 ice line. Alternatively, comet C/2016 R2 (PanSTARRS) could be the fragment of a large and differentiated transneptunian object, with properties characteristic of volatile-enriched layers.

Impact of sulfate on the solubility of Tc(IV) in acidic to hyperalkaline aqueous reducing systems

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Sarah B. Duckworth ◽  
Xavier Gaona ◽  
Alexander Baumann ◽  
Kathy Dardenne ◽  
Jörg Rothe ◽  
...  
Keyword(s):  
Solid Phase ◽  
Correction Factors ◽  
Mixed Salt ◽  
Ph Values ◽  
Reducing Conditions ◽  
Upper Limits ◽  
Salt Systems ◽  
Amorphous Character ◽  
Good Agreement

Abstract The solubility of 99Tc(IV) was investigated from undersaturation conditions in NaCl–Na2SO4 (0.3 M ≤ I ≤ 5.0 M), MgCl2–MgSO4 (I = 13.5 M) and CaCl2–CaSO4 (I = 13.5 M) systems with 0.001 M ≤ [SO4 2−]tot ≤ 1.0 M and 1 ≤ pH m  ≤ 12 (with pH m  = −log[H+], in molal units). Reducing conditions were set by either Sn(II) or Fe(0). Special efforts were dedicated to accurately characterize the correction factors A m required for the determination of pH m from the experimentally measured pH values in the mixed salt systems investigated, with pH m  = pHexp + A m . The combination of (pe + pH m ) measurements with Pourbaix diagrams of Tc suggests that technetium is present in its +IV redox state. This hypothesis is confirmed by XANES, which unambiguously shows the predominance of Tc(IV) both in the aqueous and solid phases of selected solubility samples. XRD and SEM–EDS support the amorphous character of the solid phase controlling the solubility of Tc(IV). EXAFS data confirm the predominance of TcO2(am, hyd) at pH m  > 1.5, whereas the formation of a Tc(IV)–O–Cl solid phase is hinted at lower pHm values in concentrated NaCl–Na2SO4 systems with ≈5 M NaCl. Solubility data collected in sulfate-containing systems are generally in good agreement with previous solubility studies conducted in sulfate-free NaCl, MgCl2 and CaCl2 solutions of analogous ionic strength. Although the complexation of Tc(IV) with sulfate cannot be completely ruled out, these results strongly support that, if occurring, complexation must be weak and has no significant impact on the solubility of Tc(IV) in dilute up to highly saline media. Solubility upper-limits determined in this work can be used for source term estimations including the effect of sulfate in a variety of geochemical conditions relevant in the context of nuclear waste disposal.

scholarly journals Reliability of temperature determination from curve-fitting in multi-wavelength pyrometery

2013 ◽  
Vol 31 (2) ◽  
pp. 333-336
Author(s):  
P.A. Ni ◽  
R.M. More ◽  
F.M. Bieniosek
Keyword(s):  
Ion Beam ◽  
Dense Matter ◽  
Warm Dense Matter ◽  
Emission Data ◽  
Reliable Determination ◽  
Temperature Determination ◽  
Multi Wavelength ◽  
Fitting In ◽  
Hot Surface

AbstractThis paper examines the reliability of a widely used method for temperature determination by multi-wavelength pyrometry. In recent warm dense matter experiments with ion-beam heated metal foils, we found that the statistical quality of the fit to the measured data is not necessarily a measure of the accuracy of the inferred temperature. We found a specific example where a second-best fit leads to a more realistic temperature value. The physics issue is the wavelength-dependent emissivity of the hot surface. We discuss improvements of the multi-frequency pyrometry technique, which will give a more reliable determination of the temperature from emission data.

scholarly journals Determination of standards of raw timber natural losses due to shrinkage at long-term dry storage

2021 ◽  
Vol 67 (No. 5) ◽  
pp. 195-203
Author(s):  
Dalibor Šafařík ◽  
Petra Hlaváčková ◽  
David Březina
Keyword(s):  
Woody Plants ◽  
Mean Value ◽  
The Czech Republic ◽  
Long Term Storage ◽  
Upper Limits ◽  
Natural Losses ◽  
Term Storage

The aim of the article is to describe the issue of determining the characteristics and parameters of raw timber natural losses due to shrinkage at long-term storage, defining the theoretical basis for creating standards, and verify its finding by means of a case study in raw timber storing. This issue is very topical in forestry practice in the Czech Republic as well as in other countries. The lower and upper limits of the standards were calculated, and the proposed mean value was grouped according to woody plants that reflected the most frequent commercial usage with respect to subsequent processing. Subsequently, experimental verification was carried out on a representative sample of 2 209.99 m3 of raw timber of Norway spruce (Picea abies /L./ H. Karst.) at selected forest administrations. Furthermore, the article addresses the related accounting and tax issues of the standards of natural losses of raw timber. Currently, no legislation mandates an entity to establish standards.

scholarly journals Imaging the disc rim and a moving close-in companion candidate in the pre-transitional disc of V1247 Orionis

2018 ◽  
Vol 621 ◽  
pp. A7 ◽  
Author(s):  
Matthew Willson ◽  
Stefan Kraus ◽  
Jacques Kluska ◽  
John D. Monnier ◽  
Michel Cure ◽  
...  
Keyword(s):  
Dust Emission ◽  
Three Dimensional ◽  
Position Angle ◽  
Asymmetric Structures ◽  
North East ◽  
The North ◽  
Band Emission ◽  
Upper Limits ◽  
Multi Wavelength ◽  
Differential Imaging

Context. V1247 Orionis harbours a pre-transitional disc with a partially cleared gap. Earlier interferometric and polarimetric observations revealed strong asymmetries both in the gap region and in the outer disc. The presence of a companion was inferred to explain these asymmetric structures and the ongoing disc clearing. Aims. Using an extensive set of multi-wavelength and multi-epoch observations we aimed to identify the origin of the previously detected asymmetries. Methods. We have observed V1247 Ori at three epochs spanning ~678 days using sparse aperture masking interferometry with Keck/NIRC2 and VLT/NACO. In addition, we search for signs of accretion through VLT/SPHERE-ZIMPOL spectral differential imaging in Hα and R-band continuum. Our SMA sub-millimetre interferometry in 880 μm continuum and in the CO(3-2) line allows us to constrain the orientation and direction of rotation of the outer disc. Results. We find the L′-band emission to be dominated by static features which trace forward-scattered dust emission from the inner edge of the outer disc located to the north-east. In H- and K-bands, we see evidence for a companion candidate that moved systematically by 45° within the first ~345 days. The separation of the companion candidate is not well constrained, but the observed position angle change is consistent with Keplerian motion of a body located on a 6 au orbit. From the SMA CO moment map, the location of the disc rim, and the detected orbital motion, we deduced the three-dimensional orientation of the disc. We see no indication of accretion in Hα and set upper limits for an accreting companion. Conclusions. The measured contrast of the companion candidate in H and K is consistent with an actively accreting protoplanet. Hence, we identify V1247 Ori as a unique laboratory for studying companion–disc interactions and disc clearing.

Determination of upper limits for spatial energy diffusion in ruby

1979 ◽  
Vol 20 (10) ◽  
pp. 4145-4149 ◽  
Author(s):  
P. F. Liao ◽  
L. M. Humphrey ◽  
D. M. Bloom ◽  
S. Geschwind
Keyword(s):  
Energy Diffusion ◽  
Upper Limits
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