Gaia Data Release 1 Lindegren, L; Lammers, U; Bastian, U ...
Astronomy and astrophysics (Berlin),
11/2016, Letnik:
595
Journal Article
Recenzirano
Odprti dostop
Context. Gaia Data Release 1 (DR1) contains astrometric results for more than 1 billion stars brighter than magnitude 20.7 based on observations collected by the Gaia satellite during the first 14 ...months of its operational phase. Aims. We give a brief overview of the astrometric content of the data release and of the model assumptions, data processing, and validation of the results. Methods. For stars in common with the Hipparcos and Tycho-2 catalogues, complete astrometric single-star solutions are obtained by incorporating positional information from the earlier catalogues. For other stars only their positions are obtained, essentially by neglecting their proper motions and parallaxes. The results are validated by an analysis of the residuals, through special validation runs, and by comparison with external data. Results. For about two million of the brighter stars (down to magnitude ~11.5) we obtain positions, parallaxes, and proper motions to Hipparcos-type precision or better. For these stars, systematic errors depending for example on position and colour are at a level of + or - 0.3 milliarcsecond (mas). For the remaining stars we obtain positions at epoch J2015.0 accurate to ~10 mas. Positions and proper motions are given in a reference frame that is aligned with the International Celestial Reference Frame (ICRF) to better than 0.1 mas at epoch J2015.0, and non-rotating with respect to ICRF to within 0.03 mas yr super(-1). The Hipparcos reference frame is found to rotate with respect to the Gaia DR1 frame at a rate of 0.24 mas yr super(-1). Conclusions. Based on less than a quarter of the nominal mission length and on very provisional and incomplete calibrations, the quality and completeness of the astrometric data in Gaia DR1 are far from what is expected for the final mission products. The present results nevertheless represent a huge improvement in the available fundamental stellar data and practical definition of the optical reference frame.
Gaia Data Release 1 Mignard, F; Klioner, S; Lindegren, L ...
Astronomy and astrophysics (Berlin),
11/2016, Letnik:
595
Journal Article
Recenzirano
Odprti dostop
Context. As part of the data processing for Gaia Data Release 1 (Gaia DR1) a special astrometric solution was computed, the so-called auxiliary quasar solution. This gives positions for selected ...extragalactic objects, including radio sources in the second realisation of the International Celestial Reference Frame (ICRF2) that have optical counterparts bright enough to be observed with Gaia. A subset of these positions was used to align the positional reference frame of Gaia DR1 with the ICRF2. Although the auxiliary quasar solution was important for internal validation and calibration purposes, the resulting positions are in general not published in Gaia DR1. Aims. We describe the properties of the Gaia auxiliary quasar solution for a subset of sources matched to ICRF2, and compare their optical and radio positions at the sub-mas level. Methods. Descriptive statistics are used to characterise the optical data for the ICRF sources and the optical-radio differences. The most discrepant cases are examined using online resources to find possible alternative explanations than a physical optical-radio offset of the quasars. Results. In the auxiliary quasar solution 2191 sources have good optical positions matched to ICRF2 sources with high probability. Their formal standard errors are better than 0.76 milliarcsec (mas) for 50% of the sources and better than 3.35 mas for 90%. Optical magnitudes are obtained in Gaia's unfiltered photometric G band. The Gaia results for these sources are given as a separate table in Gaia DR1. The comparison with the radio positions of the defining sources shows no systematic differences larger than a few tenths of a mas. The fraction of questionable solutions, not readily accounted for by the statistics, is less than 6%. Normalised differences have extended tails requiring case-by-case investigations for around 100 sources, but we have not seen any difference indisputably linked to an optical-radio offset in the sources. Conclusions. With less than a quarter of the data expected from the nominal mission it has been possible to obtain positions at the sub-mas level for most of the ICRF sources having an optical counterpart brighter than 20.5 mag.
The reactivity of Cp*Ga (Cp* = C
5
Me
5
) towards phosphanylidenephosphoranes of the type
Ar
TerP(PMe
3
) (
Ar
Ter =
Dip
Ter 2,6-(2,6-iPr
2
C
6
H
3
)
2
C
6
H
3
),
Tip
Ter 2,6-(2,4,6-iPr
3
C
6
H
2
)
2
...C
6
H
3
was investigated. While no thermal reaction was observed (in line with DFT results), irradiation at 405 nm at low temperatures resulted in the formation of phosphagallenes
Dip
TerP = GaCp* (
1a
) and
Tip
TerP = GaCp* (
1b
) accompanied by release of PMe
3
. When warming the reaction mixture to ambient temperatures without irradiation, the clean re-formation of
Ar
TerP(PMe
3
) and Cp*Ga in a second-order reaction was observed. Upon removal of PMe
3
,
1a
and
1b
were isolated and fully characterized. Both derivatives were found to be labile and decomposed to the phosphafluorenes
2a
and
2b
, indicating generation of the transient phosphinidene
Ar
TerP along with Cp*Ga. First reactivity studies show that CO
2
and H
2
O cleanly reacted with
1a
, affording
Dip
TerPCO (
3
) and
Dip
TerPH
2
(
4
), respectively.
Gallaphosphenes in the spotlight: a photochemically induced PMe
3
for Cp*Ga exchange at the phosphinidenes
Ar
TerP gives rise to the formation of gallaphosphenes, which is fully reversible when the lights are off.
Abstract
The aim of this study was to determine the carcass characteristics, meat quality, and fatty acid composition of wild-living mallards. The experimental materials comprised 30 mallards (1:1 ...sex ratio) harvested during the hunting season in northeastern Poland. The carcasses were transported to the laboratory where they were weighed individually, plucked, dressed, and dissected. The proximate chemical composition and physicochemical properties of meat and the fatty acid profile of breast muscle lipids were determined, and a histological analysis was performed. Body weight (BW) and carcass weight were higher in males than in females (P ≤ 0.05), whereas the percentage share of carcass tissue components was similar in both sexes. Edible components accounted for approximately 60% (♂) to 60.7% (♀) of the total BW of mallards, including lean meat; 40.9% (♂) to 41.5% (♀), skin with subcutaneous fat; 10.7% (♂) to 10.8% (♀), and giblets; 8.3% (♂) to 8.4% (♀). Breast muscles had high protein content (23.51%♀ to 23.6% ♂) and low fat content (0.82% ♂ to 0.84% ♀). In the fatty acid profile of breast muscle lipids, saturated fatty acids (SFA) accounted for 39.1% (♂) to 39.04% (♀), monounsaturated fatty acids (MUFA)-for 17.31% (♂) to 17.33% (♀) and polyunsaturated fatty acids (PUFA)-for 43.61% (♀) to 43.64% (♂). The diameters of type IIA and type IIB muscle fibers were lower in males than in females (P ≤ 0.05), whereas lipid storage sites in muscles were similar in both sexes. The values of cooking loss (CL), water-holding capacity (WHC), pH24, and color parameters of breast meat were comparable in males and females. The results of this study indicate that wild-living mallards, both males and females, are characterized by high meat quality, and that seasonal mallard harvests can provide meat with desirable eating attributes, attractive to consumers.
We describe powders of SrSi2O2N2:Eu2+ green phosphor synthesized with various reactive agents in a wide range of concentration. Two approaches are described, the first is adding carbonate reactive ...agents (K2CO3 and Li2CO3) to the initial powders excessively and, the second, using SrF2 reactive agent as an additional Sr source to increase the reactivity. XRD and particle size distribution analysis elucidated several additional phases in the final phosphors and revealed changes of powder morphology, including the presence of particle agglomerates. The studies of emission and excitation spectra, emission quantum efficiency and thermal quenching as well as thermoluminescence, supported by the calculations of trap depths and parameters of the electron–phonon interaction, bring a comprehensive insight into the influence of reactive agents on the SrSi2O2N2:Eu2+ phosphor.
•Fabrication of highly efficient oxynitride phosphor powders with usage of reactive agents.•Calculations of trap depths and the electron-vibrational interaction parameters.•Relationship between phase composition and photoluminescence properties.•Oxynitride phosphor solid state synthesis issues.
•Role of oxygen to nitrogen ratio in SrSi2O2N2:Eu2+ phosphors synthesis.•Discussion on the multicomposition effect on photoluminescent properties.•Solid state synthesis of strontium oxynitride ...phosphor powders.
In this study phosphor powders with the nominal composition of Sr0.98Eu0.02Si2O(5–1.5x)Nx (x in the range of 1.33–2.66) was successfully synthesized through the conventional solid-state reaction method. We carried out studies on the N3- and O2- ions effects on the structural and photoluminescent properties of the resultant oxonitridosilicates by varying nitrogen content in the initial mixture of materials. Discussion on the multicomposition effect on the luminescent properties is provided since the specimen with the bi-phase composition shows the highest quantum yield (QY) among the examined specimens. We found that luminescence peaked at 540 nm is related to Eu2+ located in the triclinic phase SrSi2O2N2. It is shown that QY of the single triclinic phase materials is relatively low. We related low QY to absorption of excitation light by uncontrolled defects. We found that the sample where the ratio of Si in silica to Si in silicon nitride is 0.5:1.5 has high QY equal to 0.68. This sample is a mixture of two phases: the triclinic phase SrSi2O2N2 and another crystal lattice, the most likely Sr3Si6O9N4. We can relate the parasite defects to the surface states in the triclinic lattice, which in the case of existence, the Sr3Si6O9N4 phase are removed.
A new receiver for the South Pole Telescope, SPT-3G, was deployed in early 2017 to map the cosmic microwave background at 95, 150, and 220 GHz with
∼
16,000 detectors, 10 times more than its ...predecessor SPTpol. The increase in detector count is made possible by lenslet-coupled trichroic polarization-sensitive pixels fabricated at Argonne National Laboratory, new 68
×
frequency-domain multiplexing readout electronics, and a higher-throughput optical design. The enhanced sensitivity of SPT-3G will enable a wide range of results including constraints on primordial B-mode polarization, measurements of gravitational lensing of the CMB, and a galaxy cluster survey. Here we present an overview of the instrument and its science objectives, highlighting its measured performance and plans for the upcoming 2018 observing season.
Europium doped oxynitride phosphors Sr1−xEuxSi2O2N2 (x = 0.04), without and with 3 and 5wt% Na2CO3 as a fluxing agent were made by a solid state reaction method at 1450°C for 4h in a flowing nitrogen ...atmosphere. It has been found that addition of flux results in a lower crystallinity and reduction of phosphor particles diameter to the average level of 8µm.
Analysis of the emission spectra indicates, that they show broad emission bands covering the whole visible range upon UV excitation and that the emission band peaks at 540nm, without a detectable blue or red shift. The variation in flux concentration proved, that a substantial, four times improvement of the photoluminescence properties were obtained for the sample made with 5wt% of Na2CO3 addition. Thermal quenching studies elucidated, that for those samples made with a flux the T1/2 point was not reached before 500K apart from the notably temperature quenching. This finding proves the economically attractive method for manufacturing strontium oxynitride phosphor with an excellent emission characteristic and a reasonable thermal quenching temperature for application in LEDs.
In this study, a series of Ca
9
Y(PO
4
)
7
compounds doped with 5% of Eu ions and with different Y/Ca ratios was synthesized using the Pechini method. Due to the presence of two different cations in ...the studied matrix (Ca
2+
and Y
3+
) that are available for europium substitution, the synthesis parameters were selected to obtain the incorporation of the europium ions (5% mol) into the calcium sites only. The phase composition as well as elemental analysis and the spectroscopic measurements, carried out before and/or after the reduction of Eu
3+
were performed to characterize the obtained phosphors. The XRD patterns show that in all cases the obtained materials consist of pure phase of Ca
9
Y(PO
4
)
7
. PLE and PL spectra measured before the reduction indicate that for the materials with the excess of yttrium, an additional Eu
3+
site is observed which was not observed for materials with a deficiency of yttrium. For samples obtained after the reduction, the luminescence of Eu
2+
depends on the changes of the Y/Ca ratio. The observed differences in Eu
2+
luminescence are discussed taking into account the creation of different compensation defects depending on change of the Y/Ca ratio.
In this study, a series of Ca
9
Y(PO
4
)
7
compounds doped with 5% of Eu ions and with different Y/Ca ratios was synthesized using the Pechini method.
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