MCNPX simulations of the response of the extended-range rem meter WENDI-2

Proton therapy uses proton beams with energies typically between 50 and 230 MeV to treat cancerous tumors very efficiently, while protecting as much as possible surrounding healthy tissues from radiation damage. Protons interacting with matter inevitably induce secondary radiation from which all people inside the proton therapy center have to be protected. The ambient dose equivalent H*(10) in such a facility is mainly due to neutrons, which can have energies up to 230 MeV. Although various dose monitoring systems sensitive to high energy neutrons have already been developed, the response function of these detectors is often insufficiently characterized, and so are the calibration factors appropriate for the specific neutron spectra encountered inside a proton therapy facility. In this work, the Monte Carlo code MCNPX 2.5.0 has been used to study the response function of the extended-range rem-meter WENDI-2 from thermal energies up to 5 GeV. A good match has been obtained with equivalent simulation results found in literature. As a first step towards the characterization of the WENDI-2 response in continuous neutron fields, MCNPX simulations have also been carried out for the case-study of a bunker around an 18 MeV H-cyclotron, which involves neutron fields from thermal energies up to 18 MeV

Optimization of the gas flow in a GEM chamber and development of the GEM foil stretcher

The gas electron multiplier technology has been proven to tolerate rat e larger than 50 MHz/cm2 without noticeable aging and to provide sub resolution on working chambers up to 45 cm x 45 cm. A new gas electron multiplier-based tracker is under development for the Hall A upgrade at Jefferson Lab. The chambers of the tracker have been designed in a modular way: each chamber consists of 3 adjacent gas electron multiplier modules, with an active area of 40 cm x 50 cm each. We optimized the gas flow inside the gas electron multiplier module volume, using the COMSOL physics simulator framework; the COMSOL-based analysis includes the design of the inlet and outlet pipes and the maximization of the uniformity of the gas flow. We have defined the procedures for the assembling of the gas electron multiplier modules and designed a mechanical system (TENDIGEM) that will be used to stretch the GEM foils at the proper tension (few kg/cm); the TENDIGEM is based on the original design developed at LNF

Query-based biclustering of gene expression data using Probabilistic Relational Models

Background: With the availability of large scale expression compendia it is now possible to view own findings in the light of what is already available and retrieve genes with an expression profile similar to a set of genes of interest (i.e., a query or seed set) for a subset of conditions. To that end, a query-based strategy is needed that maximally exploits the coexpression behaviour of the seed genes to guide the biclustering, but that at the same time is robust against the presence of noisy genes in the seed set as seed genes are often assumed, but not guaranteed to be coexpressed in the queried compendium. Therefore, we developed ProBic, a query-based biclustering strategy based on Probabilistic Relational Models (PRMs) that exploits the use of prior distributions to extract the information contained within the seed set.status: publishe

Mitochondrial mosaics in the liver of 3 infants with mtDNA defects

<p>Abstract</p> <p>Background</p> <p>In muscle cytochrome oxidase (COX) negative fibers (mitochondrial mosaics) have often been visualized.</p> <p>Methods</p> <p>COX activity staining of liver for light and electron microscopy, muscle stains, blue native gel electrophoresis and activity assays of respiratory chain proteins, their immunolocalisation, mitochondrial and nuclear DNA analysis.</p> <p>Results</p> <p>Three unrelated infants showed a mitochondrial mosaic in the liver after staining for COX activity, i.e. hepatocytes with strongly reactive mitochondria were found adjacent to cells with many negative, or barely reactive, mitochondria. Deficiency was most severe in the patient diagnosed with Pearson syndrome. Ragged-red fibers were absent in muscle biopsies of all patients. Enzyme biochemistry was not diagnostic in muscle, fibroblasts and lymphocytes. Blue native gel electrophoresis of liver tissue, but not of muscle, demonstrated a decreased activity of complex IV; in both muscle and liver subcomplexes of complex V were seen. Immunocytochemistry of complex IV confirmed the mosaic pattern in two livers, but not in fibroblasts. MRI of the brain revealed severe white matter cavitation in the Pearson case, but only slight cortical atrophy in the Alpers-Huttenlocher patient, and a normal image in the 3rd. MtDNA in leucocytes showed a common deletion in 50% of the mtDNA molecules of the Pearson patient. In the patient diagnosed with Alpers-Huttenlocher syndrome, mtDNA was depleted for 60% in muscle. In the 3rd patient muscular and hepatic mtDNA was depleted for more than 70%. Mutations in the nuclear encoded gene of <it>POLG </it>were subsequently found in both the 2nd and 3rd patients.</p> <p>Conclusion</p> <p>Histoenzymatic COX staining of a liver biopsy is fast and yields crucial data about the pathogenesis; it indicates whether mtDNA should be assayed. Each time a mitochondrial disorder is suspected and muscle data are non-diagnostic, a liver biopsy should be recommended. Mosaics are probably more frequent than observed until now. A novel pathogenic mutation in <it>POLG </it>is reported.</p> <p>Tentative explanations for the mitochondrial mosaics are, in one patient, unequal partition of mutated mitochondria during mitoses, and in two others, an interaction between products of several genes required for mtDNA maintenance.</p

De tuin, een groengrijze zone

status: publishe

Reassessment of stopping power ratio uncertainties caused by mean excitation energies using a water-based formalism

PURPOSE: In proton therapy planning, the accuracy of the Stopping Power Ratios (SPR) calculated in the stoichiometric CT calibration is affected by, among others, uncertainties on the mean excitation energies (I-values) of human tissues and water. Traditionally, the contribution of these uncertainties on the SPR has been conservatively estimated of the order of 1% or more for a reference tissue of known composition. This study provides a methodology that enables a finer estimation of this uncertainty, eventually showing that the traditional estimates of the uncertainty are too conservative. METHODS: Since human tissues contain water, a correlation exists between the I-values of tissues and water. As the SPR is the ratio of the tissue stopping power to that of water, this correlation decreases the uncertainty of the SPR. Our formalism considers this by expressing the I-value of the tissue as a function of the water weight fraction and the I-value of water, while applying Bragg's additivity rule only to the nonaqueous mixture of the tissue. For 22 reference tissue compositions, the SPR uncertainty was estimated by randomly sampling Gaussian distributions, based on ICRU data, for the I-values of water and the nonaqueous mixture, as well as for the water weight fraction. RESULTS: The relative standard deviation of the SPR, estimated at 150 MeV, is in the range of 0.1%-0.3% for soft tissues with an average water weight percentage of at least 60%. For tissues with a low water content (e.g., adipose and bones), this uncertainty is in the range of 0.5%-0.7%. CONCLUSION: Uncertainties on the I-values of human tissues and water appear to have a significantly lower impact on the SPR uncertainty than traditionally expected. In the future, this may provide a rationale for using smaller distal and proximal margins on the target volume, provided that all other range uncertainty components are correctly estimated too.status: publishe

SUPMAP : het aanbod van illegale drugs in België : wat weten we? Een haalbaarheidsstudie van betrouwbare indicatoren voor het drugsaanbod

Een evenwichtig drugsbeleid start met een grondige kennis van zowel de aanbodzijde als van de vraagzijde. Wat weten politie, justitie, douane, labo’s toxicologie en andere relevante diensten over de Belgische drugsmarkt? In dit onderzoek proberen we dit in kaart te brengen. Kennis is macht, zeker in het drugsbeleid. Op het niveau van de drugsvraagzijde werden reeds verschillende indicatoren ontwikkeld, die zowel op nationaal als op Europees niveau (EMCDDA) worden gebruikt. Indicatoren voor de aanbodzijde (de drugsmarkten) werden tot nu toe aanzienlijk minder onderzocht, en de kennis met betrekking tot indicatoren om het drugsaanbod te monitoren is eerder beperkt. Wie zijn de sleutelfiguren voor het monitoren van het drugsaanbod? Welke indicatoren kunnen er voor de verschillende echelons van de drugsmarkten (productie, import, groothandel, tussenhandel en retail) geïdentificeerd worden? Wat zijn haalbare indicatoren? Wat is de waarde van indicatoren zoals inbeslagnames, prijs en kwaliteit? Hoe kan druggerelateerde criminaliteit worden gemonitord binnen de bestaande registratiesystemen? Het antwoord op deze -en andere- vragen kunt u terugvinden in dit boek. Aan de hand van een literatuurstudie en een bevraging van de Belgische law enforcement community en de labo’s toxicologie, worden in dit onderzoek de mogelijke indicatoren geïdentificeerd en gecontroleerd op hun haalbaarheid. Aanvullend worden de internationale literatuur en wetenschappelijke bevindingen over drugsmarkten afgetoetst aan de Belgische realiteit

Optimization of the gas flow in a GEM chamber and development of the GEM foil stretcher

The gas electron multiplier technology has been proven to tolerate rat e larger than 50 MHz/cm2 without noticeable aging and to provide sub resolution on working chambers up to 45 cm x 45 cm. A new gas electron multiplier-based tracker is under development for the Hall A upgrade at Jefferson Lab. The chambers of the tracker have been designed in a modular way: each chamber consists of 3 adjacent gas electron multiplier modules, with an active area of 40 cm x 50 cm each. We optimized the gas flow inside the gas electron multiplier module volume, using the COMSOL physics simulator framework; the COMSOL-based analysis includes the design of the inlet and outlet pipes and the maximization of the uniformity of the gas flow. We have defined the procedures for the assembling of the gas electron multiplier modules and designed a mechanical system (TENDIGEM) that will be used to stretch the GEM foils at the proper tension (few kg/cm); the TENDIGEM is based on the original design developed at LNF

Diets containing N-3 fatty acids-enriched pork: effect on blood lipids, oxidative status and atherosclerosis in rabbits

Animal products enriched with n-3 fatty acids (FA) are receiving increasing interest because of the health benefits attributed to these FA. However, responses to the intake of enriched productswith different n-3 fatty acid sources have not been properly assessed. Rabbits were fed a pelleted diet simulating a meat-based adult human diet. The meat fatty acid profile was steered by feeding pigs a diet with linseed or fish oil. Significant changes in the fatty acid profile of different tissues and blood were found in the rabbits. During the experiment, the total cholesterol (TC)/high-density lipoprotein (HDL)-cholesterol (HDL-C) ratio decreased and the TC/low-density lipoprotein (LDL)-cholesterol (LDL-C) ratio increased in the fish oil pork group, while for the linseed oil pork group the TC/HDL-C ratio increased and no effect was measured for the TC/LDL-C ratio. The oxidative status was altered by the dietary treatments compared with the baseline and atherosclerosis developed during the experiment, but no differences between the two feeding groups were found

Analysis and optimization of substitution treatment in Belgium (SUBANOP)

Since the Belgian Federal Drug policy note in 2001, a legal framework has been developed for the prescription and administration of opioid substitution treatment (OST). However, until today policymakers and fieldworkers point at various gaps in the knowledge on substitution treatment in Belgium, in particular regarding substitution treatment in settings outside specialized centres, on the characteristics of clients receiving substitution therapy and on challenges and obstacles in the provision of this type of treatment. This research tries to answer these questions by providing an extensive and up-to-date overview of key elements of substitution treatment in Belgium. How is the provision of OST organized in Belgium (availability, types of providers, spread, referral and psychosocial support)? How do the clients receiving OST experience substitution treatment? Which obstacles can be identified and which recommendations can be made to overcome these obstacles? The answers to these questions can be found in this book