Two non-destructive neutron inspection techniques: prompt gamma-ray activation analysis and cold neutron tomography

Deux techniques d’inspection non-destructives utilisant des faisceaux de neutrons froids ont été développées à la source de neutrons SINQ de l’Institut Paul Scherrer : (1) l’analyse par activation neutronique prompte (PGAA) et (2) la tomographie neutronique. L’analyse par PGA (Prompt Gamma-ray Activation) est une méthode nucléaire qui permet de déterminer la concentration d’éléments présents dans un échantillon. Cette technique consiste à détecter les rayons gamma prompts émis par l’échantillon suite à des réactions de captures neutroniques. L’installation PGA à SINQ a été conçue, construite et testée par le prof. J. Kern et la Dr. M. Crittin. Cette thèse propose une nouvelle approche analytique, nommée la standardisation du k0, qui permet d’obtenir une meilleure précision dans la détermination des concentrations. Cette méthode a été utilisée tout d’abord pour mesurer la quantité de bore dans des solutions aqueuses. Puis, la mesure de matériaux de référence a prouvé la validité de la méthode pour des analyses multiélémentaires. Finalement, divers échantillons provenant de domaines très variés tels que l’archéologie, la géologie, la médecine, l’industrie nucléaire et la science des matériaux, ont été étudiés avec cette technique. Le PGAA s’est révélé particulièrement important pour l’analyse de l’hydrogène et du bore qui sont difficilement mesurables avec d’autres techniques. En outre, une lentille à neutrons a permis de déterminer la distribution bidimensionnelle d’éléments dans un échantillon provenant d’un réacteur naturel. La première partie de cette thèse décrit la technique et les résultats de l’analyse par PGA. Une installation de tomographie utilisant des neutrons froids a été développée en collaboration avec l’Université de Gand (Belgique) sur la même ligne de faisceau que le système PGA, les deux instruments étant utilisés de façon alternée. La tomographie neutronique est semblable à la tomographie par rayons X, laquelle est couramment utilisée dans les sciences médicales et l’industrie. Comme celle-ci, elle fournit des informations tridimensionnelles sur la structure des échantillons. Cependant, comme les processus d’interaction des neutrons et des rayons X avec la matière sont différents, les informations fournies sont complémentaires. Contrairement aux rayons X, les neutrons pénètrent facilement la plupart des métaux, ce qui permet d’améliorer le contraste des éléments légers. Par ailleurs, les neutrons froids rendent possible l’étude de matériaux métalliques encore plus denses. L’installation comprenait une table de rotation et un détecteur, lequel était composé d’un scintillateur et d’une caméra CCD. La résolution, qui était limitée par la divergence du guide de neutrons (L/D = 70), était d’environ 0.24 mm dans des conditions optimales. En outre, un dispositif permettant de sélectionner la vitesse des neutrons a été utilisé pour des expériences de radiographie et de tomographie nécessitant des faisceaux monochromatiques. Finalement, différentes études ont porté sur des objets provenant de la géologie, l’archéologie, la médecine dentaire, l’industrie nucléaire et l’aérospatiale. Cette technique et ses résultats font l’objet de la deuxième partie de cette thèse.Two non-destructive inspection techniques employing both cold neutron beams have been developed at the Swiss spallation source SINQ of the Paul Scherrer Institute: (1) prompt gamma-ray activation analysis (PGAA) and (2) neutron tomography. PGAA is a nuclear analytical method for identifying and quantifying simultaneously the elements contained in a sample. The technique consists in detecting capture gamma rays emitted by the target material during neutron irradiation. The PGA facility at SINQ was designed, constructed, and tested by Prof. J. Kern and Dr. M. Crittin. In the present work, a new analytical approach, namely the k0- standardization, has been studied and applied to obtain higher accuracies in the determination of element concentrations. First, this method has been applied successfully for quantitative determination of boron in aqueous solutions. Then, standard reference materials were analyzed to assess the accuracy of the method for multielement determination. Finally, the technique was applied to various samples from archeology, geology, medicine, nuclear industry and material science. Of particular interest was the concentration determination of hydrogen and boron, two elements that are difficult to measure with other techniques. Besides, a neutron focusing capillary lens was used to measure element concentrations in two-dimensional array across the surface of a bulky sample from a natural reactor. A description of the PGAA technique and of some results is presented in the first part of this thesis. A new cold neutron tomography set-up was developed at SINQ in collaboration with the University of Ghent (Belgium) with the objective to complement the existing thermal neutron radiography station. The new device was set up at the same beam line as the PGA instrument so that the two facilities were employed alternately. Neutron tomography is similar to X-ray tomography, which is widely used in medicine and industry. It provides three-dimensional information on the inner structure of a sample. As a result of the differences between neutron and X-ray interaction mechanisms, complementary information is provided by the two techniques. Unlike X-rays, neutrons have the prominent ability to penetrate most metals easily while delivering a high contrast for many light elements. Besides, if cold neutrons are used, thicker sections of metallic materials can be inspected. The whole tomography system consisted of a rotation table and an imaging device, which was based on a scintillator converting the neutron beam to a light image viewed with a CCD camera. The achievable resolution was limited by the inherent divergence of the neutron guide (L/D = 70) and was about 0.24 mm under optimal conditions. Furthermore, a neutron velocity selector was used to perform radiography and tomography experiments with monochromatic neutron beams. Finally, examinations were performed on objects covering a broad range of application fields, such as geology, dentistry, archeology, nuclear industry and aerospatial industry. A detailed presentation of the cold neutron tomography set-up and some results obtained with this technique are given in the second part of this thesis

Labeled Images Verification Using Gaussian Mixture Models

ABSTRACT We are proposing in this paper an automated system to verify that images are correctly associated to labels. The novelty of the system is in the use of Gaussian Mixture Models (GMMs) as statistical modeling scheme as well as in several improvements introduced specifically for the verification task. Our approach is evaluated using the Caltech 101 database. Starting from an initial baseline system providing an equal error rate of 27.4%, we show that the rate of errors can be reduced down to 13% by introducing several optimizations of the system. The advantage of the approach lies in the fact that basically any object can be generically and blindly modeled with limited supervision. A potential target application could be a post-filtering of images returned by search engines to prune out or reorder less relevant images

Tryptic phosphopeptides from whole casein. I. Preparation and analysis by fast protein liquid chromatography

Tryptic phosphopeptides were obtained from whole bovine casein by chromatography on the anion exchange resin QAE-Sephadex A 25. Salt gradient elution of the column allowed separation of non-phosphorylated peptides from phosphorylated species. The preparations obtained contained at least seven distinct phosphopeptides of which the following casein fragments were identified: αs1(43-58):2P, αs1(59-79): 5P, αs2(46-70): 4P, β(1-28): 4P, β(2-28): 4P, and β(33-48): 1P. Fast protein liquid chromatography (FPLC) on Mono Q HR 5/5 resin showed that the phosphopeptides were eluted in the same order as from the QAE-Sephadex resin. However, on the analytical column HR 5/5 the fragments αs1(59-79): 5P and β(2-28): 4P, having the same net charge under the conditions of chromatography, co-eluted, whereas they were at least partly separated on the preparative column HR 16/10. Following enzymic dephosphorylation, the peptides eluted at lower salt strength in the gradient. FPLC on Mono Q resin thus permitted dephosphorylation to be monitored and intermediates between the parent species and the fully dephosphorylated peptide to be identifie

Monte Carlo simulation of a whole-body counter using IGOR phantoms

Whole-body counting is a technique of choice for assessing the intake of gamma-emitting radionuclides. An appropriate calibration is necessary, which is done either by experimental measurement or by Monte Carlo (MC) calculation. The aim of this work was to validate a MC model for calibrating whole-body counters (WBCs) by comparing the results of computations with measurements performed on an anthropomorphic phantom and to investigate the effect of a change in phantom's position on the WBC counting sensitivity. GEANT MC code was used for the calculations, and an IGOR phantom loaded with several types of radionuclides was used for the experimental measurements. The results show a reasonable agreement between measurements and MC computation. A 1-cm error in phantom positioning changes the activity estimation by >2 %. Considering that a 5-cm deviation of the positioning of the phantom may occur in a realistic counting scenario, this implies that the uncertainty of the activity measured by a WBC is ∼10-20

Biokinetics and dosimetry of 111In-DOTA-NOC-ATE compared with 111In-DTPA-octreotide

Purpose: The biokinetics and dosimetry of 111In-DOTA-NOC-ATE (NOCATE), a high-affinity ligand of SSTR-2 and SSTR-5, and 111In-DTPA-octreotide (Octreoscan™, OCTREO) were compared in the same patients. Methods: Seventeen patients (10 men, 7 women; mean age 60years), referred for an OCTREO scan for imaging of a neuroendocrine tumour (15), thymoma (1) or medullary thyroid carcinoma (1), agreed to undergo a second study with NOCATE. Whole-body anterior-posterior scans were recorded 0.5 (100% reference scan), 4, 24 and 48h (17 patients) and 120h (5 patients) after injection. In 16 patients the OCTREO scan (178 ± 15MBq) was performed 16 ± 5days before the NOCATE scan (108 ± 14MBq) with identical timing; 1 patient had the NOCATE scan before the OCTREO scan. Blood samples were obtained from 14 patients 5min to 48h after injection. Activities expressed as percent of the initial (reference) activity in the whole body, lung, kidney, liver, spleen and blood were fitted to biexponential or single exponential functions. Dosimetry was performed using OLINDA/EXM. Results: Initial whole-body, lung and kidney activities were similar, but retention of NOCATE was higher than that of OCTREO. Liver and spleen uptakes of NOCATE were higher from the start (p < 0.001) and remained so over time. Whole-body activity showed similar α and β half-lives, but the β fraction of NOCATE was double that of OCTREO. Blood T 1/2β for NOCATE was longer (19 vs. 6h). As a result, the effective dose of NOCATE (105μSv/MBq) exceeded that of OCTREO (52μSv/MBq), and the latter result was similar to the ICRP 106 value of 54μSv/MBq. Differential activity measurement in blood cells and plasma showed an average of <5% of NOCATE and OCTREO attached to globular blood components. Conclusion: NOCATE showed a slower clearance from normal tissues and its effective dose was roughly double that of OCTRE

Biokinetics and dosimetry of (111)In-DOTA-NOC-ATE compared with (111)In-DTPA-octreotide.

PURPOSE: The biokinetics and dosimetry of (111)In-DOTA-NOC-ATE (NOCATE), a high-affinity ligand of SSTR-2 and SSTR-5, and (111)In-DTPA-octreotide (Octreoscan?, OCTREO) were compared in the same patients. METHODS: Seventeen patients (10 men, 7 women; mean age 60 years), referred for an OCTREO scan for imaging of a neuroendocrine tumour (15), thymoma (1) or medullary thyroid carcinoma (1), agreed to undergo a second study with NOCATE. Whole-body anterior-posterior scans were recorded 0.5 (100 % reference scan), 4, 24 and 48 h (17 patients) and 120 h (5 patients) after injection. In 16 patients the OCTREO scan (178 ± 15 MBq) was performed 16 ± 5 days before the NOCATE scan (108 ± 14 MBq) with identical timing; 1 patient had the NOCATE scan before the OCTREO scan. Blood samples were obtained from 14 patients 5 min to 48 h after injection. Activities expressed as percent of the initial (reference) activity in the whole body, lung, kidney, liver, spleen and blood were fitted to biexponential or single exponential functions. Dosimetry was performed using OLINDA/EXM. RESULTS: Initial whole-body, lung and kidney activities were similar, but retention of NOCATE was higher than that of OCTREO. Liver and spleen uptakes of NOCATE were higher from the start (p &lt; 0.001) and remained so over time. Whole-body activity showed similar α and β half-lives, but the β fraction of NOCATE was double that of OCTREO. Blood T (1/2)β for NOCATE was longer (19 vs. 6 h). As a result, the effective dose of NOCATE (105 μSv/MBq) exceeded that of OCTREO (52 μSv/MBq), and the latter result was similar to the ICRP 106 value of 54 μSv/MBq. Differential activity measurement in blood cells and plasma showed an average of &lt;5 % of NOCATE and OCTREO attached to globular blood components. CONCLUSION: NOCATE showed a slower clearance from normal tissues and its effective dose was roughly double that of OCTREO

A united statement of the global chiropractic research community against the pseudoscientific claim that chiropractic care boosts immunity.

BACKGROUND: In the midst of the coronavirus pandemic, the International Chiropractors Association (ICA) posted reports claiming that chiropractic care can impact the immune system. These claims clash with recommendations from the World Health Organization and World Federation of Chiropractic. We discuss the scientific validity of the claims made in these ICA reports. MAIN BODY: We reviewed the two reports posted by the ICA on their website on March 20 and March 28, 2020. We explored the method used to develop the claim that chiropractic adjustments impact the immune system and discuss the scientific merit of that claim. We provide a response to the ICA reports and explain why this claim lacks scientific credibility and is dangerous to the public. More than 150 researchers from 11 countries reviewed and endorsed our response. CONCLUSION: In their reports, the ICA provided no valid clinical scientific evidence that chiropractic care can impact the immune system. We call on regulatory authorities and professional leaders to take robust political and regulatory action against those claiming that chiropractic adjustments have a clinical impact on the immune system