The proton light yield of liquid scintillators is an important property in the context of their use in large-scale neutrino experiments, with direct implications for neutrino-proton scattering ...measurements and the discrimination of fast neutrons from inverse
β
-decay coincidence signals. This work presents the first measurement of the proton light yield of a water-based liquid scintillator (WbLS) formulated from 5% linear alkyl benzene (LAB), at energies below 20 MeV, as well as a measurement of the proton light yield of a pure LAB + 2 g/L 2,5-diphenyloxazole (PPO) mixture (LABPPO). The measurements were performed using a double time-of-flight method and a pulsed neutron beam from the 88-Inch Cyclotron at Lawrence Berkeley National Laboratory. The proton light yields were measured relative to that of a 477 keV electron. The relative proton light yield of WbLS was approximately 3.8% lower than that of LABPPO, itself exhibiting a relative proton light yield 15–20% higher than previous measurements of an analogous anoxic sample. The observed quenching is not compatible with the Birks model for either material, but is well described with the addition of Chou’s bimolecular quenching term.
Summary Background LDL cholesterol (LDL-C) is a well established risk factor for cardiovascular disease. Proprotein convertase subtilisin/kexin type 9 (PCSK9) binds LDL receptors, targeting them for ...degradation. We therefore assessed the efficacy, safety, and tolerability of AMG 145, a human monoclonal IgG2 antibody against PCSK9, in stable patients with hypercholesterolemia on a statin. Methods In a phase 2, dose-ranging study done in 78 centres in the USA, Canada, Denmark, Hungary, and Czech Republic, patients (aged 18–80 years) with LDL-C greater than 2·2 mmol/L on a stable dose of statin (with or without ezetimibe), were randomly assigned equally, through an interactive voice response system, to subcutaneous injections of AMG 145 70 mg, 105 mg, or 140 mg, or matching placebo every 2 weeks; or subcutaneous injections of AMG 145 280 mg, 350 mg, or 420 mg, or matching placebo every 4 weeks. Everyone was masked to treatment assignment within the every 2 weeks and every 4 weeks schedules. The primary endpoint was the percentage change in LDL-C concentration from baseline after 12 weeks. Analysis was by modified intention to treat. This study is registered with ClinicalTrials.gov , number NCT01380730. Findings 631 patients with hypercholesterolaemia were randomly assigned to AMG 145 70 mg (n=79), 105 mg (n=79), or 140 mg (n=78), or matching placebo (n=78) every 2 weeks; or AMG 145 280 mg (n=79), 350 mg (n=79), and 420 mg (n=80), and matching placebo (n=79) every 4 weeks. At the end of the dosing interval at week 12, the mean LDL-C concentrations were reduced generally dose dependently by AMG 145 every 2 weeks (ranging from 41·8% to 66·1%; p<0·0001 for each dose vs placebo) and AMG 145 every 4 weeks (ranging from 41·8% to 50·3%; p<0·0001). No treatment-related serious adverse events occurred. The frequencies of treatment-related adverse events were similar in the AMG 145 and placebo groups (39 8% of 474 vs 11 7% of 155); none of these events were severe or life-threatening. Interpretation The results suggest that PCSK9 inhibition could be a new model in lipid management. Inhibition of PCSK9 warrants assessment in phase 3 clinical trials. Funding Amgen.
Vitrification of solid technological waste is currently under investigation. For this type of waste made up of metals, minerals, and organic matters, formulation studies were carried out in the NCAS ...(Na2O–CaO–Al2O3–SiO2) system in order to define a vitrifying additive to treat the entire waste deposit, while maximizing the waste loading. Main challenge related to this type of waste comes from the presence of alumina in very large quantities in the glass/glass–ceramics melt, enhancing the risk of melt solidification due to a fast and massive crystallization. Melt lock‐up can potentially occur at the operating temperature envisaged for the process (1400°C) and is prohibitive because it would lead to a premature stoppage of the process. The results obtained from casting tests, rheological experiments, and thermodynamic modeling enabled to provide an accurate estimation of the risk of melt lock‐up for NCAS compositions. It was highlighted that the composition had a major influence on the temperature at which massive crystallization might occur. From all the results obtained, the maximum Al2O3 content that could be incorporated in the final material was determined to be close to 50 wt%. The composition of a vitrifying additive was also statistically designed to treat the technological waste of interest.
The vitrification is a possible treatment for the conditioning of the metallic Long-Lived Intermediate-Level nuclear waste. This process is characterised by the presence of immiscible oxide and ...metallic liquids that react each other. A thermodynamic model using the Calphad method is then required to predict the composition of the treated waste and the speciation of uranium in this complex system. The quaternary Cu-Fe-Si-U is chosen as the most representative to describe the metallic liquids that appear at high temperature. Key sub-systems of this quaternary are experimentally investigated and thermodynamically modelled. The description of the liquidus in the Si-rich corner of the binary Cu-Si is improved. The Cu-U is assessed with the Calphad method for the first time; it is characterised by a large miscibility gap in the liquid phase. Some new ternary isotherms of the ternary Cu-Fe-Si are then proposed: a large liquid miscibility gap appears also in this system in agreement with the observed behaviour of the metallic liquid during the experimental investigations. The Cu-Si-U system is characterised by three ternary intermetallic compounds: CuSiU, Cu2Si2U and Cu4Si4U3. A first description is proposed, but more data are still required to improve the thermodynamic modelling of this system.
•The re-assessment of Cu-Si shows an improvement in the description of the liquidus.•The new Cu-Fe-Si model predicts well the appearance of the liquid miscibility gap.•The first Calphad assessment of Cu-U and Cu-Si-U is proposed.
The solubility of hafnium dioxide (HfO2), used as a surrogate for tetravalent uranium, is measured in glass melts belonging to the CaO-Al2O3-SiO2 and Na2O-CaO-Al2O3-SiO2 systems, under oxidizing and ...reducing conditions. Two methods have been carried out to determine it and the kinetic factors controlling the HfO2 dissolution in glass melt have been investigated in order to approach equilibrium. The solubility ranges from 3 to 6.5mol% HfO2 in aluminosilicate glasses at temperature between 1250°C and 1400°C, and is not affected by the redox conditions. Conversely, the solubility is modified by the melting temperature and the glass composition. The excess of alkalis or alkaline earths which are not involved in the charge balance of AlO4 tetrahedrons in the silica network appears to play a significant role. Glass homogeneity is checked by scanning electron microscopy and X-ray diffraction. HfO2, HfSiO4, Ca2HfSi4O12, Na4Hf2(SiO4)3 and Na2HfSi2O7 are metastable crystals observed in the glass melts. The stability of those crystalline phases mainly depends on the glass composition.
•Hafnium solubility determination in soda-lime aluminosilicate glasses•Effect of glass composition, temperature and redox conditions on hafnium solubility•Description of hafnium crystallization in soda-lime aluminosilicate melts
This study focused on the electroreduction process of uranium cations in molten fluorides. It involved cyclic voltammetry, chronopotentiometry with and without current reversal, and square wave ...voltammetry.
The results indicate a two-step reduction process for uranium(IV). The first step U(IV)/U(III) exchanging one electron corresponds to a soluble/soluble system and is limited by U(IV) diffusion with
D
U(IV)
=
1.25
±
0.35
×
10
−5
cm
2
s
−1 in LiF–NaF at 720
°C.
In order to perform a thorough study of the second step U(III)/U(0) in the reduction process, the melt was chemically reduced in U(III) with U metal as reducing agent. Alternatively to the use of LiF–NaF where U metal is unstable at 720
°C, the chemical reduction of U(IV) in U(III) was performed in a LiF–CaF
2–UF
4 solution containing U metal at 810
°C. It has been confirmed that the reduction of U(III) proceeds in one step exchanging three electrons and by a diffusion controlled process with
D
U(III)
=
2.2
±
0.7
×
10
−5
cm
2
s
−1 in LiF–CaF
2 at 810
°C.
The activity coefficient of neodymium in liquid aluminium phase has been determined potentiometrically in the temperature range of 973–1073
K. To the author's knowledge, no data on this parameter has ...been published yet.
Three different electrochemical methods have been tested: the cyclic voltammetry technique, the coulometric additions method and the direct use of an Al–Nd alloy. In addition, an experimental set-up has been designed which allows working with small amounts of solvent (30
g). The molten eutectic mixture CaCl
2–NaCl (52–48
mol%) has been selected as the electrolyte.
From the results obtained, the variation of the activity coefficient of Nd in Al(l) as a function of the temperature can be expressed as follows: log
γ
Nd(Al)
=
9.81
−
17134/
T(K), in the range 973–1073
K. It has been found a good agreement between the activity coefficient values obtained from the different methods tested. Hence, it can be stated that either of the techniques used allows determining reliable values for the activity coefficient.
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Co-precipitations of cerium (III) and neodymium (III) at 10wt.% in LiCl–CaCl2 (30-70mol%) molten salt at 705°C have been achieved using an original way of precipitation, wet argon ...sparging. Several CeCl3/NdCl3 ratios have been studied, and the isolated powders were analyzed using different characterization methods including XRD investigations. The lanthanides precipitation yields have been determined around 99.9% using ICP-AES analysis. XRD demonstrated that the precipitates mainly contained mixed oxychloride (Ce1−xNdx)OCl and a small amount of the mixed oxide Ce1−yNdyO2−0.5y. Calcination of these precipitates has resulted in the cerium and neodymium mixed oxides. For the precipitation with a Ce/Nd=50/50 ratio, an hydroxychloride Ln(OH)2Cl and the oxychloride CeIV(Nd0.7Ce0.3)IIIO3Cl have been identified as unexpected intermediate compounds.
Organic scintillators doped with capture agents provide a detectable signal for neutrons over a broad energy range. This work characterizes the fast and slow neutron response of EJ-254, an organic ...plastic scintillator with 5% natural boron loading by weight. For fast neutrons, the primary mechanism for light generation in organic scintillators is n-p elastic scattering. To study the fast neutron response, the proton light yield of EJ-254 was measured at the 88-Inch Cyclotron at Lawrence Berkeley National Laboratory. Using a broadspectrum neutron source and a double time-of-flight technique, the EJ-254 proton light yield was obtained over the energy range of approximately 270 keV to 4.5 MeV and determined to be in agreement with other plastic scintillators comprised of the same polymer base. To isolate the slow neutron response, an AmBe source with polyethylene moderator was made incident on the EJ-254 scintillator surrounded by an array of EJ-309 observation detectors. Events in the EJ-254 target coincident with the signature 477.6 keV γ ray (resulting from deexcitation of the residual 7 Li nucleus following boron neutron capture) were identified. Pulse shape discrimination was used to evaluate the temporal differences in the response of EJ-254 scintillation signals arising from γ-ray and fast/slow neutron interactions. Clear separation between γ-ray and fast neutron signals was not achieved and the neutron-capture feature was observed to overlap both the γ-ray and fast neutron bands. Taking into account the electron light nonproportionality, the neutron-capture light yield in EJ-254 was determined to be 89.4 ± 1.1 keVee.
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