Quoted Uncertainty Research Articles

Improving metallicity estimates for very metal-poor stars in the Gaia DR3 GSP-Spec catalog

Context. In the latest Gaia Data Release (DR3), the GSP-Spec module has provided stellar parameters and chemical abundances measured from the RVS spectra alone. However, the GSP-Spec parameters – including metallicity – for very metal-poor (VMP; [Fe/H] < −2) stars suffer from parameter degeneracy due to a lack of information in their spectra, and are therefore affected by a large measurement uncertainty and systematic offset. Furthermore, the recommended quality cuts filter out the majority (~80%) of the VMP stars because some of them are confused with hot stars or with cool K- and M-type giants, for which the current pipeline is known to have problems. Aims. We aim to provide more precise metallicity estimates for VMP stars analyzed by the GSP-Spec module by taking photometric information into account in the analysis and breaking the degeneracy. Methods. We reanalyzed FGK-type stars in the GSP-Spec catalog by computing the Ca triplet equivalent widths from the published set of GSP-Spec stellar parameters. We compared these recovered equivalent widths with the values directly measured from public Gaia RVS spectra and investigated the precision of the recovered values and the parameter range within which the recovered values are reliable. We then converted the recovered equivalent widths to metallicities by adopting photometric temperatures and surface gravities that we derive based on Gaia and 2MASS catalogs. Results. The recovered equivalent widths agree with the directly measured values with a scatter of 0.05 dex for the stars that pass the GSP-Spec quality cuts. Among the stars recommended for filtering out, we observe a similar scatter for FGK-type stars initially misidentified as hot stars. Contrarily, we find a poorer agreement, in general, for stars that the GSP-Spec identifies as cool K- and M-type giants, although we can still define subsets that show reasonable agreement. At the low-metallicity end ([Fe/H] < −1.5), our metallicity estimates have a typical uncertainty of 0.18 dex, which is about half of the quoted GSP-Spec metallicity uncertainty at the same metallicity. Our metallicities also show better agreement with the high-resolution literature values than the original GSP-Spec metallicities at low metallicity; the scatter in the comparison decreases from 0.36–0.46 dex to 0.17−0.29 dex for stars that satisfy the GSP-Spec quality cuts. While the GSP-Spec metallicities show increasing scatter when misidentified “hot” stars and the subsets of the “cool K- and M-type giants” are included (up to 1.06 dex), we can now identify them as FGK-type stars and provide metallicities that show a small scatter in the comparisons (up to 0.34 dex), which helps us to increase the number of VMP stars with reliable and precise metallicity. Conclusions. The inclusion of photometric information greatly contributes to breaking parameter degeneracy, enabling precise metallicity estimates for VMP stars from Gaia RVS spectra. We produce a publicly available catalog of bright metal-poor stars suitable for high-resolution follow-up. The sample contains about 2345 VMP stars with an estimated contamination rate of 5%.

Long-term continuous monitoring of methane emissions at an oil and gas facility using a multi-open-path laser dispersion spectrometer

A method for methane emissions monitoring at industrial facility level was developed based on a high precision multi-open-path laser dispersion spectrometer combined with Bayesian analysis algorithms using Monte Carlo Markov Chain (MCMC) inference. From the methane path-averaged concentrations spatially distributed over the facility under study, together with the wind vector, the analysis allows detection, localization and quantification of fugitive methane emissions. This paper describes the very first long term (3 months), continuous (24 h/7 days) deployment of this monitoring system at an operational gas processing and distribution facility. The continuous monitoring system, made of the combination of the open-path high-precision (<10 ppb) methane concentration analyser and the data analysis method, was evaluated with controlled releases of methane of about 5 kg/h for short periods of time (30–60 min). Quantification was successful, with actual emission rates lying well within the quoted uncertainty ranges. Source localisation was found to lack accuracy, with biases of 30–50 m in the direction of the line of sight of the spectrometer, due to the short duration of the controlled releases, the limited wind vector diversity, and complications from air flows around buildings not accounted for by the transport model. Using longer-term data from the deployment, the MCMC algorithm led to the identification of unexpected low intensity persistent sources (<1 kg/h) at the site. Localisation of persistent sources was mostly successful at equipment level (within ~20 m) as confirmed by a subsequent survey with an optical gas imaging (OGI) camera. Quantification of these individual sources was challenging owing to their low intensity, but a consistent estimate of the total methane emission from the facility could be derived using two different inference approaches. These results represent a stepping stone in the development of continuous monitoring systems for methane emissions, pivotal in driving greenhouse gas reduction from industrial facilities. The demonstrated continuous monitoring system gives promising performance in early detection of unexpected emissions and quantification of potentially time-varying emissions from an entire facility.

No detectable redox exchange between sulfur and iron during rapid cooling of basalts

The valence states of iron and sulfur in mantle-derived melts influence and respond to the composition of the mantle as well as the subsequent evolution of those melts in Earth's crust. Characterizing the valence states of iron and sulfur in silicate melts that have quenched to form glasses is therefore critical to understanding the composition of the mantle and the magmatic processes that take place before and during volcanic eruptions. Glasses quenched from silicate melts offer the opportunity to precisely measure sulfur and iron valence states, but whether the transition from melt to glass affects the valence state of sulfur and iron is uncertain. Here, we use the glassy margins of two pillow basalts, one from a mid-ocean ridge and one from a back-arc basin, as a natural experiment to test the effect of quench rate on sulfur and iron valence states. We report micro-X-ray Absorption Near Edge Structure (XANES) measurements of S6+/ΣS (S6+/[S6++S2−]) and Fe3+/ΣFe (Fe3+/[Fe2++Fe3+]) along transects from the rapidly quenched rims of the pillows down into the slowly cooled crystal-rich interiors. The range of average quench rates estimated for our selected analysis areas range from 1.2×105°C/sec at the pillow margin to 1.1°C/sec in the interior and span quench rates experienced by natural and experimental glasses. On average, S6+/ΣS = 0.09±0.01 and Fe3+/ΣFe = 0.147±0.002 in the mid-ocean ridge sample and S6+/ΣS = 0.21±0.01and Fe3+/ΣFe = 0.153±0.004 in the back-arc sample, where the quoted uncertainty is the 1σ standard deviation of n= 9-16 analyses. We find that the S6+/ΣS and Fe3+/ΣFe values along transects in each sample show no systematic changes with depth, and by proxy, no systematic changes with quench rate. In each pillow, all measured S6+/ΣS and Fe3+/ΣFe ratios are within the absolute uncertainty of each technique. We propose that these observations are consistent with either sluggish reaction kinetics between sulfur and iron, or an insignificant temperature effect on sulfur-iron redox exchange equilibria. These observations demonstrate that sulfur and iron valence states in glasses with varying quench rates can be directly compared, and that changes in sulfur and iron valence during quench are below the limits of detection with XANES.

THE IAEA FORENSICS PROGRAM: RESULTS OF THE AMS 14C INTERCOMPARISON EXERCISE ON CONTEMPORARY WINES AND COFFEES

ABSTRACTIn the frame of the IAEA-CRP (Coordinated Research Projects): Enhancing Nuclear Analytical Techniques to Meet the Needs of Forensic Sciences, an intercomparison exercise was organized between three AMS laboratories. Aim of the program is to promote the use of nuclear and accelerator-based techniques in routine forensics practice. In this view, one of the key points is the assessment of the precision and accuracy levels achievable on material of forensic interest. We review the general structure and status of the project, with emphasis on results obtained in the analysis of wines of different grape varieties and grounded coffee beans from different locations such as Brazil, Spain, and Italy. The three laboratories processed the samples according to different chemical protocols and performed the 14C measurements using different systems: MICADAS in Zurich and Debrecen and a HVEE 4130HC 3 MV Tandetron in Lecce. Within the quoted uncertainty, the results showed good reproducibility, indicating that uncertainty level of the order of 0.3% are achieved by AMS on a single sample while multiple sample analyses results in precision down to 0.1–0.2%. The measured 14C concentrations on coffee and wine samples resulted to be consistent with atmospheric 14C levels in the growing years.

Measurement of the branching fraction of Λc+→pω decay at Belle

Using 980.6 $\rm fb^{-1}$ of data collected with the Belle detector operating at the KEKB asymmetric-energy $e^+e^-$ collider, we present a measurement of the branching fraction of the singly Cabibbo-suppressed decay $\Lambda_c^+ \to p \omega$. A clear $\Lambda_c^+$ signal is observed for $\Lambda_c^+ \to p \omega$ with a statistical significance of 9.1 standard deviations, and we measure the ratio of branching fractions ${\cal B}(\Lambda_c^+ \to p \omega)/{\cal B}(\Lambda_c^+ \to p K^- \pi^+) = (1.32 \pm 0.12 (\rm stat) \pm 0.10 (\rm syst))\times 10^{-2}$, from which we infer the branching fraction ${\cal B}(\Lambda_c^+ \to p \omega) = (8.27 \pm 0.75 (\rm stat) \pm 0.62 (\rm syst) \pm 0.42 (\rm ref))\times 10^{-4}$. The first quoted uncertainty is statistical, the second systematic, and the third from the reference mode $\Lambda_c^+ \to p K^- \pi^+$.

Kinetic fall-off behavior for the Cl + Furan-2,5-dione (C4H2O3, maleic anhydride) reaction.

Rate coefficients, k, for the gas-phase Cl + Furan-2,5-dione (C4H2O3, maleic anhydride) reaction were measured over the 15-500 torr (He and N2 bath gas) pressure range at temperatures between 283 and 323 K. Kinetic measurements were performed using pulsed laser photolysis (PLP) to produce Cl atoms and atomic resonance fluorescence (RF) to monitor the Cl atom temporal profile. Complementary relative rate (RR) measurements were performed at 296 K and 620 torr pressure (syn. air) and found to be in good agreement with the absolute measurements. A Troe-type fall-off fit of the temperature and pressure dependence yielded the following rate coefficient parameters: ko(T) = (9.4 ± 0.5) × 10-29 (T/298)-6.3 cm6 molecule-2 s-1, k∞(T) = (3.4 ± 0.5) × 10-11 (T/298)-1.4 cm3 molecule-1 s-1. The formation of a Cl·C4H2O3 adduct intermediate was deduced from the Cl atom temporal profiles and an equilibrium constant, KP(T), for the Cl + C4H2O3 ↔ Cl·C4H2O3 reaction was determined. A third-law analysis yielded ΔH = -15.7 ± 0.4 kcal mol-1 with ΔS = -25.1 cal K-1 mol-1, where ΔS was derived from theoretical calculations at the B3LYP/6-311G(2d,p,d) level. In addition, the rate coefficient for the Cl·C4H2O3 + O2 reaction at 296 K was measured to be (2.83 ± 0.16) × 10-12 cm3 molecule-1 s-1, where the quoted uncertainty is the 2σ fit precision. Stable end-product molar yields of (83 ± 7), (188 ± 10), and (65 ± 10)% were measured for CO, CO2, and HC(O)Cl, respectively, in an air bath gas. An atmospheric degradation mechanism for C4H2O3 is proposed based on the observed product yields and theoretical calculations of ring-opening pathways and activation barrier energies at the CBS-QB3 level of theory.

On the ATLAS top mass measurements and the potential for stealth stop contamination

The discovery of the stop — the Supersymmetric partner of the top quark — is a key goal of the physics program enabled by the Large Hadron Collider. Although much of the accessible parameter space has already been probed, all current searches assume the top mass is known. This is relevant for the “stealth stop” regime, which is characterized by decay kinematics that force the final state top quark off its mass shell; such decays would contaminate the top mass measurements. We investigate the resulting bias imparted to the template method based ATLAS approach. A careful recasting of these results shows that effect can be as large as 2.0 GeV, comparable to the current quoted uncertainty on the top mass. Thus, a robust exploration of the stealth stop splinter requires the simultaneous consideration of the impact on the top mass. Additionally, we explore the robustness of the template technique, and point out a simple strategy for improving the methodology implemented for the semi-leptonic channel.

Validation of IRDFF-II library by means of 252Cf spectral averaged cross sections

Spectrum-averaged cross sections (SACS) is an important quantity usable in validation of nuclear cross sections. Especially in case of dosimetrical reactions there is a request on precise validation. This paper presents SACS measured in the reference 252Cf(sf) neutron field for neutron dosimetry reactions to validate recently updated IRDFF-II library intended mainly for neutron metrology applications. It covers 46Ti(n,p)46Sc, 47Ti(n,p)47Sc, 48Ti(n,p)48Sc, 58Ni(n,p)58Co, 60Ni(n,p)60Co, 58Ni(n,2n)57Ni, 24Mg(n,p)24Na, 27Al(n,α)24Na and 63Cu(n,α)60Co threshold reactions. Measurement of 60Ni(n,p)60Co SACS is included in NEA's High Priority Nuclear Data Request List since existing data are discrepant. Spectral averaged cross sections were derived from experimentally determined reaction rates by gamma spectrometry using a same high-purity germanium detector to measure all irradiated samples. Measured spectrum-averaged cross sections agree very well within quoted uncertainties with those calculated using the IRDFF-II library. No other library achieves such good performance. Thus, the presented data support use of the cross sections of the mentioned reactions from IRDFF-II library.

ExoMol molecular line lists XXXVI: X 2Π – X 2Π and A 2Σ+ – X 2Π transitions of SH

ABSTRACT The GYT line list covering rotational, rovibrational, and rovibronic transitions of the mercapto radical SH is presented. This work extends and replaces the SNaSH line list, which covers the ground (electronic) X 2Π state only. This extension is prompted by the tentative identification of the ultraviolet features of SH as being of importance in the transmission spectrum of the ultrahot Jupiter exoplanet WASP-121b. This GYT line list model is generated by fitting empirical potential energy, spin–orbit, and electronic angular momenta functions to experimentally measured wavelengths within the X 2Π and A 2Σ+ states and to the A 2Σ+–X 2Π band system using ab initio curves as a starting reference point. The fits are compatible with the quoted uncertainty of the experimental data used of ∼0.03–0.3 cm−1. The GYT line list covers wavelengths longer than 0.256 $\mu$m and includes 7686 rovibronic states and 572 145 transitions for 32SH. Line lists for the 33SH, 34SH, 36SH, and 32SD isotopologues are generated including a consideration of non-Born–Oppenheimer effects for SD. The line lists are available from the CDS (http://cdsarc.u-strasbg.fr) and ExoMol (www.exomol.com) data bases.

Application of Digital Anti-Coincidence Counting Method for Primary Activity Determination of &lt;sup&gt;59&lt;/sup&gt;Fe

As a radiopharmaceutical, the use of 59 Fe is classified as a high pharmaceutical risk product. Therefore, a standard reference for activity measurement of 59 Fe is necessary to ensure its metrological aspect. This paper describes an alternative method for primary activity determination of 59 Fe for establishing a standard reference. The 59 Fe solution was prepared using two different cocktails and measured by the 4 p b (LS)- g counting system using a digital anti-coincidence counting method with emulated live-time of the extending dead-time. A final activity results at the reference time for the two samples series are (473.32 ± 2.55) kBq/g and (477.14 ± 2.42) kBq/g with quoted uncertainty evaluated at k = 1. The final activity was compared to the value obtained from the other two coincidence counting method and found to be in a good agreement within its uncertainty value.

Rate Coefficients for the Gas-Phase Reaction of ( E)- and ( Z)-CF3CF═CFCF3 with the OH Radical and Cl-Atom.

The rate coefficients, k, for the gas-phase reaction of the OH radical and Cl-atom with ( E)- and ( Z)-CF3CF═CFCF3 were measured using a relative rate technique over a range of temperature (240-375 K) and bath gas pressure (50-630 Torr, He). The obtained rate coefficients were found to be independent of pressure under these conditions. The obtained rate coefficients for the reaction of Cl-atom with ( E)- and ( Z)-CF3CF═CFCF3 at 296 K were k1(296 K) = (7.23 ± 0.3) × 10-12 cm3 molecule-1 s-1 and k2(296 K) = (6.70 ± 0.3) × 10-12 cm3 molecule-1 s-1, respectively, with the temperature dependence described by the Arrhenius expressions: k1( T) = (3.47 ± 0.35) × 10-12 exp[(210 ± 25)/ T] cm3 molecule-1 s-1 and k2( T) = (3.37 ± 0.35) × 10-12 exp[(199 ± 25)/ T] cm3 molecule-1 s-1. The rate coefficients for the OH radical reaction with ( E)- and ( Z)-CF3CF═CFCF3 were found to be k3(296-375 K) = (4.34 ± 0.45) × 10-13 cm3 molecule-1 s-1 and k4(296-375 K) = (3.30 ± 0.35) × 10-13 cm3 molecule-1 s-1, respectively. The quoted rate coefficient uncertainties are 2σ (95% confidence level) and include estimated systematic errors. The rate coefficients for the reaction of OH with a mixture of the two stereoisomers were determined using a pulsed laser photolysis-laser-induced fluorescence (PLP-LIF) technique for comparison with previous kinetic measurements using stereoisomer mixtures. The effective rate coefficient for the 0.7/0.3 ( E)/( Z) stereoisomer sample was found to be nearly independent of temperature over the range 222-375 K with a value of (4.47 ± 0.36) × 10-13 cm3 molecule-1 s-1. The atmospheric lifetimes for ( E)- and ( Z)-CF3CF═CFCF3 due to OH-reactive loss are estimated to be 25 and 35 days, respectively. The lifetime-corrected radiative efficiencies (W m-2 ppb-1) and 100 year time horizon global warming potentials derived in this work are 0.05 and 1.2 for ( E)-CF3CF═CFCF3 and 0.13 and 4.1 for ( Z)-CF3CF═CFCF3. The photochemical ozone creation potentials for ( E)- and ( Z)-CF3CF═CFCF3 are estimated to be 2.5 and 2.1, respectively.

Timing and structure of the weak Asian Monsoon event about 73,000 years ago

Abstract Oxygen isotope (δ18O) records of cave speleothem have played an important role in the past two decades in characterizing the Asian Monsoon (AM) variability and correlating the monsoonal events with other global climate events on millennial timescales. Of a series of millennial events occurred during the last glacial period, the Chinese Stadial-20 (CS-20, corresponding to the Greenland Stadial-20, GS-20) event around ∼73 kyr BP (thousand years before present, where present = 1950 AD) is distinctive, since it is the weakest AM event during the last glacial period and is likely linked to the Toba volcanic super-eruption. While Greenland ice core records are commonly used to correlate the last glacial millennial events, yet their absolute age uncertainties around the GS-20 is larger than 1000 years. This prohibits precise correlations of the event between global climate archives from different climate systems to investigate the underlying climatic dynamics. Here, we present three Chinese cave stalagmite δ18O records from the AM region, covering a period from 76 to 71 kyr BP, across the CS-20. All stalagmites have high uranium contents and relatively fast growth rates, allowing acquisition of high-resolution (∼10 years) δ18O records with precise 230Th age controls (≤200 years, 2σ) to precisely characterize the structure and timing of the CS-20. Our results demonstrate that the onset and termination of the CS-20 are more gradual in Chinese cave records relative to the GS-20 event in Greenland ice core records. As such, we suggest a new ‘break-point’ approach to correlate CS-20 with GS-20, at either the initial onset or initial termination shifts of the events, instead of the conventional ‘mid-point’ match. We dated the initial onset and initial termination of CS-20 to ~74.0 ± 0.2 and 72.5 ± 0.2 kyr BP, respectively, confirming the Greenland ice core chronology well within the quoted uncertainty. The ‘break-point’ correlation at the GS-20/CS-20 initial termination suggests a lagged onset of CS-20 relative to the onset of GS-20. The lagged onset is in line with a northern high-latitude forcing mechanism triggering the event and a central role of oceanic reorganizations in the propagation of the climate signal. An alternative ‘break-point’ correlation at the GS-20/CS-20 initial onset suggests that the CS-20 initial termination leads the GS-20 initial termination by a few hundred years. This apparent paradox thus calls for further empirical and theoretical studies to better understand the underlying climatic dynamics and in turn the correlation strategy.

First Evidence for cos2β>0 and Resolution of the Cabibbo-Kobayashi-Maskawa Quark-Mixing Unitarity Triangle Ambiguity.

We present first evidence that the cosine of the CP-violating weak phase 2β is positive, and hence exclude trigonometric multifold solutions of the Cabibbo-Kobayashi-Maskawa (CKM) Unitarity Triangle using a time-dependent Dalitz plot analysis of B^{0}→D^{(*)}h^{0} with D→K_{S}^{0}π^{+}π^{-} decays, where h^{0}∈{π^{0},η,ω} denotes a light unflavored and neutral hadron. The measurement is performed combining the final data sets of the BABAR and Belle experiments collected at the ϒ(4S) resonance at the asymmetric-energy B factories PEP-II at SLAC and KEKB at KEK, respectively. The data samples contain (471±3)×10^{6}BB[over ¯] pairs recorded by the BABAR detector and (772±11)×10^{6}BB[over ¯] pairs recorded by the Belle detector. The results of the measurement are sin2β=0.80±0.14(stat)±0.06(syst)±0.03(model) and cos2β=0.91±0.22(stat)±0.09(syst)±0.07(model). The result for the direct measurement of the angle β of the CKM Unitarity Triangle is β=[22.5±4.4(stat)±1.2(syst)±0.6(model)]°. The measurement assumes no direct CP violation in B^{0}→D^{(*)}h^{0} decays. The quoted model uncertainties are due to the composition of the D^{0}→K_{S}^{0}π^{+}π^{-} decay amplitude model, which is newly established by performing a Dalitz plot amplitude analysis using a high-statistics e^{+}e^{-}→cc[over ¯] data sample. CP violation is observed in B^{0}→D^{(*)}h^{0} decays at the level of 5.1 standard deviations. The significance for cos2β>0 is 3.7 standard deviations. The trigonometric multifold solution π/2-β=(68.1±0.7)° is excluded at the level of 7.3 standard deviations. The measurement resolves an ambiguity in the determination of the apex of the CKM Unitarity Triangle.

Validation of selected (n,2n) dosimetry reactions in IRDFF-1.05 library

Spectrum-averaged cross sections (SACS) have been measured in the reference 252Cf(sf) neutron field for the following high-threshold (n,2n) neutron dosimetry reactions since they are especially important due to the high threshold which allows validation of upper parts of prompt fission neutron spectrum. This work includes 59Co(n,2n)58Co, 197Au(n,2n)196Au, 169Tm(n,2n)168Tm, 55Mn(n,2n)54Mn, 93Nb(n,2n)92 mNb and 89Y(n,2n)88Y and for the 59Co(n,p)59Fe threshold reactions. SACS were inferred from experimentally determined reaction rates by gamma spectrometry using a semiconductor high-purity germanium detector to measure irradiated samples. Measured reaction rates agree within quoted uncertainties with those calculated from the IRDFF-1.05 library, except for the reaction 55Mn(n,2n)54Mn, for which the measured value is underestimated by 16%. For this reaction the ENDF-B/VII.1 evaluation agrees with measured reaction rate within uncertainties.

Reference Data for the Density, Viscosity, and Surface Tension of Liquid Al–Zn, Ag–Sn, Bi–Sn, Cu–Sn, and Sn–Zn Eutectic Alloys

The data for the physicochemical properties viscosity, density, and surface tension obtained by different experimental techniques have been analyzed for liquid Al–Zn, Ag–Sn, Bi–Sn, Cu–Sn, and Sn–Zn eutectic alloys. All experimental data sets have been categorized and described by the year of publication, the technique used to obtain the data, the purity of the samples and their compositions, the quoted uncertainty, the number of data in the data set, the form of data, and the temperature range. The proposed standard deviations of liquid eutectic Al–Zn, Ag–Sn, Bi–Sn, Cu–Sn, and Sn–Zn alloys are 0.8%, 0.1%, 0.5%, 0.2%, and 0.1% for the density, 8.7%, 4.1%, 3.6%, 5.1%, and 4.0% for viscosity, and 1.0%, 0.5%, 0.3%, N/A, and 0.4% for surface tension, respectively, at a confidence level of 95%.

Global Properties of M31’s Stellar Halo from the SPLASH Survey. III. Measuring the Stellar Velocity Dispersion Profile∗

Abstract We present the velocity dispersion of red giant branch stars in M31’s halo, derived by modeling the line-of-sight velocity distribution of over 5000 stars in 50 fields spread throughout M31’s stellar halo. The data set was obtained as part of the Spectroscopic and Photometric Landscape of Andromeda’s Stellar Halo (SPLASH) Survey, and covers projected radii of 9 to 175 kpc from M31’s center. All major structural components along the line of sight in both the Milky Way (MW) and M31 are incorporated in a Gaussian Mixture Model, including all previously identified M31 tidal debris features in the observed fields. The probability that an individual star is a constituent of M31 or the MW, based on a set of empirical photometric and spectroscopic diagnostics, is included as a prior probability in the mixture model. The velocity dispersion of stars in M31’s halo is found to decrease only mildly with projected radius, from 108 km s−1 in the innermost radial bin (8.2 to 14.1 kpc) to ∼80 to 90 km s−1 at projected radii of ∼40–130 kpc, and can be parameterized with a power law of slope −0.12 ± 0.05. The quoted uncertainty on the power-law slope reflects only the precision of the method, although other sources of uncertainty we consider contribute negligibly to the overall error budget.

Improvements in world-wide intercomparison of PV module calibration

Abstract The calibration of the electrical performance of seven photovoltaic (PV) modules was compared between four reference laboratories on three continents. The devices included two samples in standard and two in high-efficiency crystalline silicon technology, two CI(G)S and one CdTe module. The reference value for each PV module parameter was calculated from the average of the results of all four laboratories, weighted by the respective measurement uncertainties. All single results were then analysed with respect to this reference value using the En number approach. For the four modules in crystalline silicon technology, the results agreed in general within ±0.5%, with all values within ±1% and all En numbers well within [−1, 1], indicating further scope for reducing quoted measurement uncertainty. Regarding the three thin-film modules, deviations were on average roughly twice as large, i.e. in general from ±1% to ±2%. A number of inconsistent results were observable, although within the 5% that can be statistically expected on the basis of the En number approach. Most inconsistencies can be traced to the preconditioning procedure of one participant, although contribution of other factors cannot be ruled out. After removing these obvious inconsistent results, only two real outliers remained, representing less than 2% of the total number of measurands. The results presented show improved agreement for the calibration of PV modules with respect to previous international exercises. For thin-film PV modules, the preconditioning of the devices prior to calibration measurements is the most critical factor for obtaining consistent results, while the measurement processes seem consistent and repeatable.

Reactor antineutrino shoulder explained by energy scale nonlinearities?

The Daya Bay, Double Chooz and RENO experiments recently observed a significant distortion in their detected reactor antineutrino spectra, being at odds with the current predictions. Although such a result suggests to revisit the current reactor antineutrino spectra modeling, an alternative scenario, which could potentially explain this anomaly, is explored in this letter. Using an appropriate statistical method, a study of the Daya Bay experiment energy scale is performed. While still being in agreement with the γ calibration data and B12 measured spectrum, it is shown that a O(1%) deviation of the energy scale reproduces the distortion observed in the Daya Bay spectrum, remaining within the quoted calibration uncertainties. Potential origins of such a deviation, which challenge the energy calibration of these detectors, are finally discussed.

Improved nickel-corrected isotopic analysis of iron using high-resolution multi-collector inductively coupled plasma mass spectrometry

Herein, we describe the use of a Nu Plasma 1700 multi-collector inductively coupled plasma mass spectrometer (MC-ICP-MS) in true high-resolution mode to determine Fe isotopic ratios at the center of Fe peaks instead of their shoulders. A standard-sample bracketing (SSB) technique and a Ni doping method were used for instrumental mass bias calibration. The effects of Fe/Ni ratio and plasma mode were investigated in order to establish a high-precision Fe isotope analysis method. The results showed that the Ni-doping method provided more precision isotopic ratios than that of the SSB technique. Moreover, this work also presents Fe isotopic compositions of some geological reference materials (BCR-2, BHVO-2, AGV-2, GSR-1, GSR-2, GSR-3, GSP-2, and DSN-1), which were highly accurate with respect to the international Fe isotope standard IRMM-014. The iron isotopic compositions of most geological reference materials measured in this study agreed with the previously published data within quoted analytical uncertainties. Long-term reproducibility analyses of all samples indicate that the obtained isotopic ratios are highly reproducible, with precisions of better than ±0.03‰ for δ56Fe (2 sd) and ±0.06‰ (2 sd) for δ57Fe. Our results demonstrated the usefulness of internal element doping for improving the stability and precision of isotope analysis by MC-ICP-MS.

Handling Overdispersion in CRONUS-Earth Intercomparison Measurements: A Bayesian Approach

AbstractThe recently completed CRONUS-Earth project broadly studied the production systematics of terrestrial in-situ cosmogenic nuclides and also incorporated an intercomparison study in which multiple labs measured various nuclides in homogenized geologic materials. Aliquots of these materials were measured in several labs for multiple nuclides, and the results combined to determine benchmark, consensus values. Results for some of these samples exhibited overdispersion, meaning that the measurements from the various labs differed by more than we would expect, given the quoted uncertainties. A traditional way to handle overdispersion is to add an extra amount to the variance of each lab. Another approach is to use a method that identifies potential outliers and then gives the outliers less weight in determining the final answer. A group of such methods is based on Bayesian thinking; one relatively simple member of this group was first proposed by Press (1997). We review the Press method and then apply it to the CRONUS data sets. We compare these results to those obtained by the added variance method and discuss the implications.