Quantifying Platinum and Palladium in Solid Ore Using Laser-Induced Breakdown Spectroscopy Assisted by the Laser-Induced Fluorescence (LIBS-LIF) Technique

The laser-induced breakdown spectroscopy assisted by laser-induced fluorescence (LIBS-LIF) in a two-step process was used to measure the concentration of platinum (Pt) and palladium (Pd) by surface analysis of a solid ore core from the Lac des Iles mine followed by analysis of the same core that was pulverized and compacted. This work focuses mainly on the measurement of Pt since the case of Pd has been extensively discussed in previous work. The excitation of Pt is performed at 235.71 nm with fluorescence emission observed near 269.84 nm. Calibration was performed with synthetic samples prepared from the same ore as the samples studied and the calibration curve shows good linearity in Pt content over several orders of magnitude. A limit of detection (LOD) of approximately 0.15 parts per million (ppm) over an average of 200 laser shots was demonstrated. In contrast, conventional LIBS provides a LOD of about 21 ppm over an average of 200 laser shots due to low signal-to-noise ratio and spectral interference from other elements and does not meet the requirements for estimating the average Pt concentration in the ore. The Pt concentrations obtained using LIBS-LIF on solid ore are generally in good agreement with those obtained in its pulverized and compacted form, as well as with laboratory measurements made by conventional chemical methods. However, the comparison of the results obtained for Pd using LIBS-LIF with the laboratory showed a less satisfactory agreement, probably due to its more inhomogeneous distribution in the ore.

Corneal biomechanical properties in myopic and emmetropic children

OBJECTIVE

The purpose of this study was to investigate the relationship between corneal biomechanics and ocular morphology in myopic children and adolescents.

PATIENTS AND METHODS

The study included 170 right eyes, from 170 patients under the age of 18 years, who underwent a complete ophthalmologic examination, gathering the following data: spherical equivalent (SE) (under pharmacological cycloplegia), biomechanical parameters - corneal hysteresis (CH) and corneal resistance factor (CRF), structural parameters - axial length (AL) and central corneal thickness (CCT).

RESULTS

The average age of the patients was 15.26 years old (55.29% girls, 44.70% boys). Out of the 170 eyes, 111 were myopic eyes and 59 were emmetropic. Myopic eyes had a significantly lower CH (p=0.001), CRF (p=0.002) and CCT (p=0.009), and higher AL (p<0.001) than emmetropic eyes. The AL and CCT were significantly higher in myopic males, compared to myopic females (p<0.001 and 0.001). In myopes, we found statistically significant negative correlations between AL and CH (Pearson's r=-0.218), CRF (r=-0.226) and also SE (r=-0.539), and positive between SE and either CH (r=0.193) or CRF (r=0.201).

CONCLUSIONS

Corneal biomechanical properties are significantly related to myopia parameters in children.

A 3D high resolution MRI method for the visualization of cardiac fibro-fatty infiltrations

Modifications of the myocardial architecture can cause abnormal electrical activity of the heart. Fibro-fatty infiltrations have been implicated in various cardiac pathologies associated with arrhythmias and sudden cardiac death, such as arrhythmogenic right ventricular cardiomyopathy (ARVC). Here, we report the development of an MRI protocol to observe these modifications at 9.4 T. Two fixed ex vivo human hearts, one healthy and one ARVC, were imaged with an Iterative decomposition with echo asymmetry and least-square estimations (IDEAL) and a magnetization transfer (MT) 3D sequences. The resulting fat fraction and MT ratio (MTR) were analyzed and compared to histological analysis of the three regions (“ARVC triangle”) primarily involved in ARVC structural remodeling. In the ARVC heart, high fat content was observed in the “ARVC triangle” and the superimposition of the MTR and fat fraction allowed the identification of fibrotic regions in areas without the presence of fat. The healthy heart exhibited twice less fat than the ARVC heart (31.9%, 28.7% and 1.3% of fat in the same regions, respectively). Localization of fat and fibrosis were confirmed by means of histology. This non-destructive approach allows the investigation of structural remodeling in human pathologies where fibrosis and/or fatty tissue infiltrations are expected to occur.

Difficulties in maintaining electroconvulsive treatment (ECT) in a psychiatric hospital during covid19 pandemic

Introduction

ECT is an effective care with high level of recommendation. During the COVID19, new recommendations to protect patients and caregivers combined with the increasing use of medicines and medical devices (MD) for anesthesia, caused greater difficulties of supply. Even if vital for patients, it is challenging to maintain ECT in this environment.

Objectives

The aim of this study is to resume the measures implemented in order to maintain ECT during COVID19.

Methods

Retrospective analysis of measures implemented to maintain the ECT during COVID19.

Results

As FFP2 masks were restricted to intensive care units, our hospital were not supplied. After negotiations, the regional health agency (ARS) has granted us an allocation of 100 masks to maintain ECT. Our efficient stock management of personal protective equipment as well as our transparency on these stocks with ARS and sharing with other hospitals out of stock played a role in this agreement.We had to adapt our MDs references according to breaks of many ones and new recommendations. The university hospital helping us in supplying certain missing references. Considering the difficulties in supplying drugs and MDs, and limited availability of anesthetists, we have reduced the number of ECT. Prioritization of patients with vital indications had to be achieved.

Conclusions

The prioritization of some services by the regulatory agency causes many supply difficulties for the others. It would be important to reassess the priority of ECT in such crisis because most of the time other caregivers and regulatory agencies are not aware how they are vital for patients.

Atmospheric Carbon Mineralization in an Industrial-Scale Chrysotile Mining Waste Pile

Magnesium-rich minerals that are abundant in ultramafic mining waste have the potential to be used as a safe and permanent sequestration solution for carbon dioxide (CO₂). Our understanding of thermo-hydro-chemical regimes that govern this reaction at an industrial scale, however, has remained an important challenge to its widespread implementation. Through a year-long monitoring experiment performed at a 110 Mt chrysotile waste pile, we have documented the existence of two distinct thermo-hydro-chemical regimes that control the ingress of CO₂ and the subsequent mineral carbonation of the waste. The experimental results are supported by a coupled free-air/porous media numerical flow and transport model that provides insights into optimization strategies to increase the efficiency of mineral sequestration at an industrial scale. Although functioning passively under less-than-optimal conditions compared to laboratory-scale experiments, the 110 Mt Thetford Mines pile is nevertheless estimated to be sequestering up to 100 tonnes of CO₂ per year, with a potential total carbon capture capacity under optimal conditions of 3 Mt. Annually, more than 100 Mt of ultramafic mine waste suitable for mineral carbonation is generated by the global mining industry. Our results show that this waste material could become a safe and permanent carbon sink for diffuse sources of CO₂.

Chemical composition and seasonal changes in the fatty acid profile of Uruguayan “Colonia” Cheeses

The basic chemical composition and the fatty acid (FA) profile of Uruguayan Colonia cheese, consumed in the Mercosur region, were determined. 24 cheeses from different dairy farms: 10 elaborated in autumn and 14 in spring, were analyzed. Those cheeses are made from cow´s milk, whose diet was composed of 50% pasture system, 25% concentrate, and 25% silage reserves. The cheese making and ripening time were similar. Seasonal differences emerged in the profiles of saturated FA (SFA), unsaturated FA (UFA) and polyunsaturated FA (PUFA). The seasonal comparation of polyunsaturated FA (PUFA) as well as the CLA isomer such as C18:2 t10c12 showed significant differences (p < 0.05). CLA isomer such as C18:2 c9t11, showed no differences (p > 0.05). The atherogenesis index (AI) = 2.21 and thrombogenicity (IT) = 2.84, were calculated and discussed.

The Impact of Thyroid Autoimmunity on the Clinical and Diabetes Parameters of Patients with Latent Autoimmune Diabetes in Adults

AIM

We evaluated the clinical and diabetes parameters of latent autoimmune diabetes in adults (LADA) patients according to the presence of thyroid autoimmunity (TA).

MATERIALS AND METHODS

Patients with LADA (diabetes onset after 30 years of age, no need for insulin treatment for at least 6 months after diabetes onset, positive for glutamic acid decarboxylase antibodies (GADA)) were evaluated for the presence of thyroid peroxidase antibodies (TPOAb) and were subjected to clinical and laboratory evaluations of the glycated hemoglobin and basal C peptide levels. The patients were stratified into either group A (with TA) or group B (without TA).

RESULTS

We evaluated 104 (57 female and 47 male) patients with LADA. The mean age at diabetes onset was 44±10 years. The prevalence of TA among the LADA patients was 28.8% (30 patients; 23 female and 7 male). In groups A and B, the mean age at diabetes onset was 41.47±10.15 and 45.07±10 years (p=0.03), the basal C peptide level was 0.69±0.16 and 1.9±1.3 ng/ml (p<0.0001), the glycated hemoglobin level was 9.8±2.2 and 9.1±2.2 (p=0.04), and the time to insulin treatment was 3.2±2.1 years and 4.98±2.2 years (p=0.038), respectively. The use of a basal bolus insulin regimen was more frequent in group A than in group B (56.7% and 35.1%, respectively; p=0.03).

CONCLUSION

TA identifies a particular phenotype of LADA displaying a higher GADA titer, lower basal C peptide levels and poorer glycemic control.

Analysis of the source term formation in a severe accident initiated by end fitting failure in CANDU type reactors

CANDU type reactors have some peculiarities in initiation and progression of severe accidents. In the present paper one of the specificities – the End Fitting Failure accident – is analysed from the point of view of source term formation. The accident is initiated by a failure of the re-fueling machine. Fuel bundles are ejected in the re-fuelling machine room and fuel elements suffer a significant fragmentation by mechanical impact and by the rapid increase of the temperature. A direct transfer of the fission products occurs directly to the containment. The source term in the containment and also the source term to the environment is calculated supposing an open venting communication to the external atmosphere. The simulation is performed by using the ASTEC code in coupled calculation CPA-IODE-ISODOPE-DOSE option. The evolution of the distributions for the most important released fission products is presented for different regions and for different hosts. The most important factors of influence on the source term formation are identified and discussed.

Chemistry aspects of the source term formation for a severe accident in a CANDU type reactor

The progression of a severe accident in a CANDU type reactor is slow because the core is surrounded by a large quantity of heavy and light water which acts as a heat sink to remove the decay heat. Therefore, the source term formation is a complex and long process involving fission products transport and releasing in the fuel matrix, thermal hydraulics of the transport fluid in the primary heat system and containment, deposition and transport of fission products, chemistry including the interaction with the dousing system, structural materials and paints, etc. The source term is strongly dependent on initial conditions and accident type. The paper presents chemistry aspects for a severe accident in a CANDU type reactor, in terms of the retention in the primary heat system. After releasing from the fuel elements, the fission products suffer a multitude of phenomena before they are partly transferred into the containment region. The most important species involved in the deposition were identified. At the same time, the influence of the break position in the transfer fractions from the primary heat system to the containment was investigated.

Uncertainty analysis for fission products transport in CANDU primary heat transport during a severe accident

The work realized under the Severe Accident Research Network of excellence (SARNET) project has shown that the SOPHAEROS module, part of Accident Source Term Evaluation Code (ASTEC) can be fully used to simulate the fission products transport and deposition phenomena in the CANDU Primary Heat Transport (PHT) system. This paper presents an uncertainty analysis for the fission products transport in the CANDU PHT system during a severe accident to obtain the domains of the output parameters, for this study masses of Caesium, Strontium and Iodine deposited in the PHT system and its nodes, taking into account the associated input parameters uncertainties. Five uncertain parameters, the starting time for the releasing process, the duration of the releasing process, the releasing fractions for Cs, Sr and I have been chosen. To generate aleatory values for the uncertain parameters, a method and software have been developed and Monte Carlo simulations to determine uncertainties propagation through the SOPHAEROS module has been carried out.

SU-E-T-499: Validation of the Varian Generic Phase Space Files for Monte Carlo Calculations of Dose Distributions for the TrueBeam Linac Head

PURPOSE

To validate the generic phase space files for Varian TrueBeam linac head simulations.

METHODS

The generic phase space files include the simulation results of 6MV, 10MV, 6MV FFF, and 10MV FFF (flattening-filter free) operating modes of TrueBeam for patient-independent linac head components. Using the generic phase space files as the radiation sources, the BEAMnrc Monte Carlo codes are used to simulate the patient-dependent parts of the TrueBeam linac and the resulting phase space files are generated at a plane just before entering a water phantom for 4 different field sizes (5×5, 10×10, 20×20, and 40×40 cm² ). Dose distributions are calculated by DOSXYZnrc in the water phantom of size 50×50×40 cm³ . The percentage-depth-dose (PDD) curves and lateral dose profiles at three different depths (dmax, 10cm, 20cm) are obtained. Comprehensive comparisons have been made for a total of 64 dose profiles (including PDDs) between the Monte Carlo calculations and the measured data. The gamma index analysis is performed for all the comparisons.

RESULTS

The matching of the calculated dose distributions to the measured ones is analyzed by the gamma index method with a criterion of 2% dose tolerance and 2 mm distance-to-agreement. Of the 64 comparisons, the minimum gamma index passing rate is at least 92%, after taking into account the statistical nature of the Monte Carlo calculated dose values. Despite the existence of latent variance of phase space files, the phantom dose calculation uncertainty can be less than 1% for field sizes as small as 5×5 cm² . The computing time saved by using phase space files could be a factor of 5-10.

CONCLUSIONS

The Varian generic phase space files are accurate and efficient radiation sources for Monte Carlo calculations of radiation dose distributions for TrueBeam linac head. This work was supported in part by Varian Medical Systems and the NIH (1R01 CA104205 and 1R21 CA153587).

Carbon sequestration kinetic and storage capacity of ultramafic mining waste

Mineral carbonation of ultramafic rocks provides an environmentally safe and permanent solution for CO(2) sequestration. In order to assess the carbonation potential of ultramafic waste material produced by industrial processing, we designed a laboratory-scale method, using a modified eudiometer, to measure continuous CO(2) consumption in samples at atmospheric pressure and near ambient temperature. The eudiometer allows monitoring the CO(2) partial pressure during mineral carbonation reactions. The maximum amount of carbonation and the reaction rate of different samples were measured in a range of experimental conditions: humidity from dry to submerged, temperatures of 21 and 33 °C, and the proportion of CO(2) in the air from 4.4 to 33.6 mol %. The most reactive samples contained ca. 8 wt % CO(2) after carbonation. The modal proportion of brucite in the mining residue is the main parameter determining maximum storage capacity of CO(2). The reaction rate depends primarily on the proportion of CO(2) in the gas mixture and secondarily on parameters controlling the diffusion of CO(2) in the sample, such as relative saturation of water in pore space. Nesquehonite was the dominant carbonate for reactions at 21 °C, whereas dypingite was most common at 33 °C.