A comparison of different approaches for the analysis of 36Cl in graphite samples.

This study compares different approaches for the quantification of the massic activity of 36Cl in graphite samples. All approaches consisted of a combustion step in combination with a trapping solution to collect the volatile elements. Two different resins were used to separate 36Cl from the matrix (CL resin and PS resin). Liquid scintillation counting (LSC), scintillation counting (SC) and tandem inductively coupled plasma mass spectrometry (ICP-MS/MS) were used to quantify 36Cl activity. The chemical yield in all approaches was determined by means of ion chromatography (IC). In addition, the methods were applied to a real activated graphite sample.

A new method based on selective fluorescent polymers (PSresin) for the analysis of 90Sr in presence of 210Pb in environmental samples.

90Sr is of major concern in emergency and environmental control plans. It is one of the main fission products in nuclear facilities and is a high-energy beta emitter that presents chemical properties similar to those of calcium. 90Sr is commonly detected using methods based on liquid scintillation counting (LSC) following a chemical separation to remove potential interferences. However, these methods generate mixed wastes (hazardous and radioactive). In recent years, an alternative strategy using PSresins has been developed. For 90Sr analysis with PSresins, 210Pb is the main interferent that should be considered, as it is also strongly retained in the PSresin. In this study, a procedure was developed involving a precipitation with iodates to separate lead from strontium before the PSresin separation. Moreover, the method developed was compared with well-established and routinely used methods based on LSC, revealing that the new method produced equivalent results in less time and with less waste generation.

Fast analysis of gross alpha with a new plastic scintillation resin.

Radionuclides analysis is a complex task, with high time and economic costs. In decommissioning activities and environmental monitoring, it is very evident, in which, to obtain an appropriate information, it is necessary to perform as many analyses as possible. The number of these analyses can be reduced using screening gross alpha or gross beta parameters. However, the currently used methods cannot give an answer as fast as it would be desired and, moreover, more than 50% of the results reported in the interlaboratory exercises fall outside the acceptance range. This work presents the development of a new material and method to gross alpha activity determination using a plastic scintillation resin (PSresin) in drinking and river water samples. A specific procedure was developed involving a new PSresin (using bis-(3-trimethylsilyl-1-propyl)-methanediphosphonic acid as an extractant) that is selective for all actinides, radium and polonium. Quantitative retention and 100% detection efficiencies were obtained at pH 2 with nitric acid. PSA value of 135 was used for α/ß discrimination. Eu was used to determine or estimate retention in sample analyses. The method developed can measure, in less than 5 h from the reception of the sample, the gross alpha parameter with quantification errors comparable or even lower to those obtained with conventional methods.

Investigation of a new approach for 36Cl determination in solid samples using plastic scintillators.

This work reports a new approach for the determination of 36Cl in radioactive waste samples from nuclear decommissioning, wherein novel plastic scintillator (PS) materials were used for the concentration of 36Cl prior to the detection with scintillation counting. Different plastic scintillator (PS) materials were tested for their selective absorption and detection of 36Cl activity in solid samples. PS microspheres (PSm), cross-linked PSm (CPSm) and PS resin have been investigated. PS resin was identified as the most suitable material for 36Cl analysis. Pyrolysis and subsequent trapping of the volatile elements in a bubbler was used. The trapping solution was finally loaded onto a cartridge of the PS resin. Scintillation counting and ion chromatography were used to determine the activity concentration and the chemical recovery, respectively.

Simultaneous determination of 210Pb and 90Sr and 210Po isolation in sludge samples using a plastic scintillation resin.

This study describes a new and fast method for separating 210Po from 210Pb and 90Sr, before simultaneously measuring the individual activities of the latter two radionuclides using a plastic scintillation resin (PSresin) in sludge samples taken from a drinking water treatment plant. This method speeds up the analysis process significantly by simultaneously measuring 210Pb and 90Sr in a single step. The method is reproducible and has a relative standard deviation of less than 25% for 210Pb, 210Po and 90Sr. The method was satisfactorily validated with an intercomparison sample and applied to sludge samples from a drinking water treatment plant. The minimum detectable activities for 0.9 g of sludge are 5.5 Bq/kg and 8 Bq/kg for 210Pb and 90Sr respectively when measured for 180 min, and 0.5 Bq/kg for 210Po when measured for 5000 min.

Development of an equipment for real-time continuous monitoring of alpha and beta radioactivity in river water.

Different regulations require the monitoring of radioactivity in the environment (e.g., 2013/51/Euratom, Real Decreto 314/2016) to protect the environment and the population from abnormal radioactivity presence caused by natural reasons or discharges or accidents in nuclear installations. Nowadays, the monitoring of α- and ß-emitting radionuclides is performed discontinuously in laboratories due to the difficulties in applying classical techniques to continuous measurements. This limits the number of samples that can be measured per day, produces high costs per analysis, and introduces a significant delay between the moment of contamination and when it is detected. Plastic scintillation microspheres (PSm) represent a new possibility for continuous measurements because water samples can flow through a bed of PSm connected to a pair of photomultipliers (PMTs), allowing continuous monitoring of the activity. This idea is the basis of the Waterrad detector, which can monitor radioactivity at environmental levels in river water. This paper describes the optimization of a detection cell containing PSm, a detection chamber as well as active and passive shielding. In its final set-up, the Waterrad detector presents a background signal of 0.23 (1) cps and detection efficiencies of 1.86(7)·10-5 cps·L·Bq-1 for 3H, 7.4(8)·10-3 cps·L·Bq-1 for 90Sr/90Y and 5.5(5)·10-3 cps·L·Bq-1 for 241Am. The detection limits in the optimum window for a counting time of 5 h were 490 Bq/L for 3H, 2.3 Bq/L for 90Sr/90Y and 3.0 Bq/L for 241Am. These values indicate that Waterrad can be used as an alarm detector for monitoring radioactivity in water at activity levels similar to those of environmental samples, making it suitable for water or waste surveillance involving a high frequency of measurements.

Analysis of isotopes of plutonium in water samples with a PSresin based on aliquat·336.

There is a necessity to have techniques capable to perform rapid determinations of specific radionuclides with the aim to provide fast response in emergency situations where a large number of samples need to be measured in a short time. Plastic Scintillation Resins (PSresins) raises as an adequate tool to achieve this purpose and in the present study a methodology to determine plutonium using a PSresin based on Aliquat·336 was developed. Different sample treatments have been studied under acidic conditions with an emphasis on valence adjustment treatment to achieve an effective retention within the PSresin. Under 3 M nitric acid conditions and an iron sulphamate (II) + nitrite valence adjustment, quantitative retention and 100% detection efficiency were achieved. The retention of the different interferences evaluated (238U, 230Th, 241Am, 210Pb and 99Tc) was low and therefore they do not interfere significantly in the determination of plutonium, except for 99Tc. Finally, a stable tracer to calculate the PSresin separation yield was studied, revealing that gold is suitable for this purpose. This procedure was applied to the analysis of spiked sea and river water samples, obtaining errors lower than 10% in their quantification.

Stalagmite-like pre-retinal deposits in the optical coherence tomography of two vitrectomy patients with panuveitis.

Two patients with panuveitis are presented in whom, after undergoing a vitrectomy, the optical coherence tomography (OCT) revealed some unusual pre-retinal hyper-reflective deposits with the shape of stalagmites, distributed in a multifocal and perivascular pattern. Case 1: 51-year-old male with panuveitis in the right eye. After diagnostic-therapeutic vitrectomy, OCT showed pre-retinal stalagmite-like deposits. There was no clear aetiology, and the deposits persisted over the time. Case 2: 76-year-old woman with panuveitis in the right eye. After a surgery for cataract-vitrectomy and epiretinal membrane peeling, OCT revealed pre-retinal stalagmite-like deposits. The analysis reported elevated Toxoplasma IgG titres. Clarithromycin and corticosteroid were prescribed, resulting in the disappearance of pre-retinal deposits. The stalagmite-like deposits are not a very common tomographic sign of a posterior uveitis process, but they seem to correlate with inflammatory activity. There does not seem to be a clear mechanism or a particular aetiology.

Depósitos prerretinianos tipo estalagmita en la tomografía de coherencia óptica de dos pacientes vitrectomizados con panuveítis / Stalagmite-like pre-retinal deposits in the optical coherence tomography of two vitrectomy patients with panuveitis

Se presentan los casos de dos pacientes con panuveítis que, tras ser vitrectomizados, presentaron en la tomografía de coherencia óptica (OCT), depósitos prerretinianos inusuales en forma de estalagmitas hiperreflectivas, multifocales y de patrón perivascular.Caso 1: Varón de 51 años con panuveítis en el ojo derecho (OD). Tras una vitrectomía diagnóstico-terapéutica, la OCT evidenció depósitos prerretinianos tipo estalagmitas, sin una etiología clara y persistencia de los depósitos.Caso 2: Mujer de 76 años con panuveítis del OD. Tras una cirugía combinada de catarata y pelado de membrana epirretiniana, la OCT reveló depósitos prerretinianos tipo estalagmitas. La analítica reportó títulos IgG elevados para toxoplasma. Se prescribió claritromicina y corticoide con desaparición progresiva de los depósitos prerretinianos.Los depósitos prerretinianos tipo estalagmitas son un signo tomográfico poco común de los procesos uveíticos posteriores, parecen correlacionarse con la actividad inflamatoria, aunque sin un claro mecanismo y sin una etiología en particular.

Two patients with panuveitis are presented in whom, after undergoing a vitrectomy, the optical coherence tomography (OCT) revealed some unusual pre-retinal hyper-reflective deposits with the shape of stalagmites, distributed in a multifocal and perivascular pattern.Case 1: 51-year-old male with panuveitis in the right eye. After diagnostic-therapeutic vitrectomy, OCT showed pre-retinal stalagmite-like deposits. There was no clear aetiology, and the deposits persisted over the time.Case 2: 76-year-old woman with panuveitis in the right eye. After a surgery for cataract-vitrectomy and epiretinal membrane peeling, OCT revealed pre-retinal stalagmite-like deposits. The analysis reported elevated Toxoplasma IgG titres. Clarithromycin and corticosteroid were prescribed, resulting in the disappearance of pre-retinal deposits.The stalagmite-like deposits are not a very common tomographic sign of a posterior uveitis process, but they seem to correlate with inflammatory activity. There does not seem to be a clear mechanism or a particular aetiology.

WhatEELS. A python-based interactive software solution for ELNES analysis combining clustering and NLLS.

The analysis of energy loss near edge structures in EELS is a powerful method for a precise characterization of elemental oxidation states and local atomic coordination with an outstanding lateral resolution, down to the atomic scale. Given the complexity and sizes of the EELS spectrum images datasets acquired by the state-of-the-art instrumentation, methods with low convergence times are usually preferred for spectral unmixing in quantitative analysis, such as multiple linear least squares fittings. Nevertheless, non-linear least squares fitting may be a superior choice for analysis in some cases, as it eliminates the need of calibrated reference spectra and provides information for each of the individual components included in the fitted model. To avoid some of the problems that the non-linear least squares algorithms may suffer dealing with mixed-composition samples and, thus, a model comprised by a large number of individual curves we proposed the combination of clustering analysis for segmentation and non-linear least squares fitting for spectral analysis. Clustering analysis is capable of a fast classification of pixels in smaller subsets divided by their spectral characteristics, and thus increases the control over the model parameters in separated regions of the samples, classified by their specific compositions. Furthermore, along with this manuscript we provide access to a self-contained and expandable modular software solution called WhatEELS. It was specifically designed to facilitate the combined use of clustering and NLLS, and includes a set of tools for white-lines analysis and elemental quantification. We successfully demonstrated its capabilities with a control sample of mesoporous cerium oxide doped with praseodymium and gadolinium, which posed challenging case-study given its spectral characteristics.

PSresin for the analysis of alpha-emitting radionuclides: Comparison of diphosphonic acid-based extractants.

The analysis of radionuclides is complex, with high economic and time costs. For this reason, there is a need to develop new methods and strategies to reduce these costs. One important group in the analysis of radionuclides is the actinides, which are the main constituents assessed in the total gross alpha together with radium and radon test used to measure radioactivity in drinking water. Moreover, in nuclear dismantling processes, the possible spread of the released radionuclides has to be controlled, which is measured by many techniques, depending on the radionuclides, through scintillation. This work presents a new method to analyse actinides using plastic scintillation resins (PSresins) packed in a solid-phase extraction cartridge. The proposed method combines chemical separation and sample measurement into a single step, reducing the effort, time and reagents required for analysis as well as decreasing the amount of waste generated. The PSresins compared in this study contained three selective extractants based on methylenediphosphonic acid with different radicals, which has a high affinity for tri-, tetra-, and hexavalent actinides in dilute acids. These extractants were immobilised on plastic scintillation microspheres at a ratio of 1/1:6, producing a retention and detection efficiency of 100% for 241Am, 230Th, Uranium and 238Pu. The retention and detection efficiency were 20% and 100%, respectively, for 210Po and low for 226Ra.

A high-entropy manganite in an ordered nanocomposite for long-term application in solid oxide cells.

The implementation of nano-engineered composite oxides opens up the way towards the development of a novel class of functional materials with enhanced electrochemical properties. Here we report on the realization of vertically aligned nanocomposites of lanthanum strontium manganite and doped ceria with straight applicability as functional layers in high-temperature energy conversion devices. By a detailed analysis using complementary state-of-the-art techniques, which include atom-probe tomography combined with oxygen isotopic exchange, we assess the local structural and electrochemical functionalities and we allow direct observation of local fast oxygen diffusion pathways. The resulting ordered mesostructure, which is characterized by a coherent, dense array of vertical interfaces, shows high electrochemically activity and suppressed dopant segregation. The latter is ascribed to spontaneous cationic intermixing enabling lattice stabilization, according to density functional theory calculations. This work highlights the relevance of local disorder and long-range arrangements for functional oxides nano-engineering and introduces an advanced method for the local analysis of mass transport phenomena.

Stalagmite-like pre-retinal deposits in the optical coherence tomography of two vitrectomy patients with panuveitis. / Depósitos prerretinianos tipo estalagmita en la tomografía de coherencia óptica de dos pacientes vitrectomizados con panuveítis.

Two patients with panuveitis are presented in whom, after undergoing a vitrectomy, the optical coherence tomography (OCT) revealed some unusual pre-retinal hyper-reflective deposits with the shape of stalagmites, distributed in a multifocal and perivascular pattern. Case 1: 51-year-old male with panuveitis in the right eye. After diagnostic-therapeutic vitrectomy, OCT showed pre-retinal stalagmite-like deposits. There was no clear aetiology, and the deposits persisted over the time. Case 2: 76-year-old woman with panuveitis in the right eye. After a surgery for cataract-vitrectomy and epiretinal membrane peeling, OCT revealed pre-retinal stalagmite-like deposits. The analysis reported elevated Toxoplasma IgG titres. Clarithromycin and corticosteroid were prescribed, resulting in the disappearance of pre-retinal deposits. The stalagmite-like deposits are not a very common tomographic sign of a posterior uveitis process, but they seem to correlate with inflammatory activity. There does not seem to be a clear mechanism or a particular aetiology.

Scaling Law Describes the Spin-Glass Response in Theory, Experiments, and Simulations.

The correlation length ξ, a key quantity in glassy dynamics, can now be precisely measured for spin glasses both in experiments and in simulations. However, known analysis methods lead to discrepancies either for large external fields or close to the glass temperature. We solve this problem by introducing a scaling law that takes into account both the magnetic field and the time-dependent spin-glass correlation length. The scaling law is successfully tested against experimental measurements in a CuMn single crystal and against large-scale simulations on the Janus II dedicated computer.

Analyzing the potential impact of BREXIT on the European research collaboration network.

In this work, we study the impact that the withdrawal of institutions from the United Kingdom caused by BREXIT has on the European research collaboration networks. To this aim, we consider BREXIT as a targeted attack to those graphs composed by the European institutions that have collaborated in research projects belonging to the three main H2020 programs (Excellent Science, Industrial Leadership, and Societal Challenges). The consequences of this attack are analyzed at the global, mesoscopic, and local scales and compared with the changes suffered by the same collaboration networks when a similar quantity of nodes is randomly removed from the network. Our results suggest that changes depend on the specific program, with Excellent Science being the most affected by BREXIT perturbation. However, the structure of the integrated collaboration network is not significantly affected by BREXIT compared to the variations observed after the random removal of institutions.

Aging Rate of Spin Glasses from Simulations Matches Experiments.

Experiments on spin glasses can now make precise measurements of the exponent z(T) governing the growth of glassy domains, while our computational capabilities allow us to make quantitative predictions for experimental scales. However, experimental and numerical values for z(T) have differed. We use new simulations on the Janus II computer to resolve this discrepancy, finding a time-dependent z(T,t_{w}), which leads to the experimental value through mild extrapolations. Furthermore, theoretical insight is gained by studying a crossover between the T=T_{c} and T=0 fixed points.

Matching Microscopic and Macroscopic Responses in Glasses.

We first reproduce on the Janus and Janus II computers a milestone experiment that measures the spin-glass coherence length through the lowering of free-energy barriers induced by the Zeeman effect. Secondly, we determine the scaling behavior that allows a quantitative analysis of a new experiment reported in the companion Letter [S. Guchhait and R. Orbach, Phys. Rev. Lett. 118, 157203 (2017)].PRLTAO0031-900710.1103/PhysRevLett.118.157203 The value of the coherence length estimated through the analysis of microscopic correlation functions turns out to be quantitatively consistent with its measurement through macroscopic response functions. Further, nonlinear susceptibilities, recently measured in glass-forming liquids, scale as powers of the same microscopic length.

Analysis of (210)Pb in water samples with plastic scintillation resins.

(210)Pb is a radioactive lead isotope present in the environment as member of the (238)U decay chain. Since it is a relatively long-lived radionuclide (T1/2 = 22.2 years), its analysis is of interest in radiation protection and the geochronology of sediments and artwork. Here, we present a method for analysing (210)Pb using plastic scintillation resins (PSresins) packaged in solid-phase extraction columns (SPE cartridge). The advantages of this method are its selectivity, the low limit of detection, as well as reductions in the amount of time and reagents required for analysis and the quantity of waste generated. The PSresins used in this study were composed of a selective extractant (4',4″(5″)-Di-tert-butyldicyclohexano-18-crown-6 in 1-octanol) covering the surface of plastic scintillation microspheres. Once the amount of extractant (1:1/4) and medium of separation (2 M HNO3) were optimised, PSresins in SPE cartridges were calibrated with a standard solution of (210)Pb. (210)Pb could be fully separated from its daughters, (210)Bi and (210)Po, with a recovery value of 91(3)% and detection efficiency of 44(3)%. Three spiked water samples (one underground and two river water samples) were analysed in triplicates with deviations lower than 10%, demonstrating the validity of the PS resin method for (210)Pb analysis.

A new plastic scintillation resin for single-step separation, concentration and measurement of technetium-99.

Technetium is a synthetic element with no stable isotopes, produced as waste in nuclear power plants and in cyclotrons used for nuclear medicine. The element has high mobility, in the form of TcO4(-); its determination is therefore important for environmental protection. Technetium is found in low concentrations and therefore common methods for its analysis include long treatments in several steps and require large amounts of reagents for its purification and preconcentration. Plastic scintillation resins (PSresin) are novel materials used to separate, preconcentrate and measure radionuclides in a single step. The objective of this study is to prepare and characterise a PSresin for the preconcentration and measurement of (99)Tc. The study first evaluates the reproducibility of the production of PSresins between batches and over time; showing good reproducibility and storage stability. Next, we studied the effect of some common non-radioactive interferences, showing small influences on measurement, and radioactive interferences ((36)Cl and (238)U/(234)U). (36)Cl can be removed by a simple treatment with 0.5 M HCl and (238)U/(234)U can be removed from the column by cleaning with a mixture of 0.1 M HNO3 and 0.1 M HF. In the latter case, a slight change in the morphology of the PSresin caused an increase in detection efficiency. Finally, the PSresin was applied to the measurement of real spiked samples (sea water and urine) with deviations lower than 10% in all cases.

Standalone ethanol micro-reformer integrated on silicon technology for onboard production of hydrogen-rich gas.

A novel design of a silicon-based micro-reformer for onboard hydrogen generation from ethanol is presented in this work. The micro-reactor is fully fabricated with mainstream MEMS technology and consists of an active low-thermal-mass structure suspended by an insulating membrane. The suspended structure includes an embedded resistive metal heater and an array of ca. 20k vertically aligned through-silicon micro-channels per square centimetre. Each micro-channel is 500 µm in length and 50 µm in diameter allowing a unique micro-reformer configuration that presents a total surface per projected area of 16 cm(2) cm(-2) and per volume of 320 cm(2) cm(-3). The walls of the micro-channels become the active surface of the micro-reformer when coated with a homogenous thin film of Rh-Pd/CeO2 catalyst. The steam reforming of ethanol under controlled temperature conditions (using the embedded heater) and using the micro-reformer as a standalone device are evaluated. Fuel conversion rates above 94% and hydrogen selectivity values of ca. 70% were obtained when using operation conditions suitable for application in micro-solid oxide fuel cells (micro-SOFCs), i.e. 750 °C and fuel flows of 0.02 mlL min(-1) (enough to feed a one watt power source).