Search for passing-through-walls neutrons constrains hidden braneworlds

In many theoretical frameworks our visible world is a $3$-brane, embedded in a multidimensional bulk, possibly coexisting with hidden braneworlds. Some works have also shown that matter swapping between braneworlds can occur. Here we report the results of an experiment - at the Institut Laue-Langevin (Grenoble, France) - designed to detect thermal neutron swapping to and from another braneworld, thus constraining the probability $p^2$ of such an event. The limit, $p<4.6\times 10^{-10}$ at $95 \%$ C.L., is $4$ orders of magnitude better than the previous bound based on the disappearance of stored ultracold neutrons. In the simplest braneworld scenario, for two parallel Planck-scale branes separated by a distance $d$, we conclude that $d>87$ in Planck length units.Comment: 5 pages, 3 figures. Published in Physics Letters

p53 and p73 display common and distinct requirements for sequence specific binding to DNA

Although p53 and p73 share considerable homology in their DNA-binding domains, there have been few studies examining their relative interactions with DNA as purified proteins. Comparing p53 and p73β proteins, our data show that zinc chelation by EDTA is significantly more detrimental to the ability of p73β than of p53 to bind DNA, most likely due to the greater effect that the loss of zinc has on the conformation of the DNA-binding domain of p73. Furthermore, prebinding to DNA strongly protects p73β but not p53 from chelation by EDTA suggesting that DNA renders the core domain of p73 less accessible to its environment. Further exploring these biochemical differences, a five-base sub-sequence was identified in the p53 consensus binding site that confers a greater DNA-binding stability on p73β than on full-length p53 in vitro. Surprisingly, p53 lacking its C-terminal non-specific DNA-binding domain (p53Δ30) demonstrates the same sequence discrimination as does p73β. In vivo, both p53 and p73β exhibit higher transactivation of a reporter with a binding site containing this sub-sequence, suggesting that lower in vitro dissociation translates to higher in vivo transactivation of sub-sequence-containing sites

Advances in Carcinogenic Metal Toxicity and Potential Molecular Markers

Metal compounds such as arsenic, cadmium, chromium, cobalt, lead, mercury, and nickel are classified as carcinogens affecting human health through occupational and environmental exposure. However, the underlying mechanisms involved in tumor formation are not well clarified. Interference of metal homeostasis may result in oxidative stress which represents an imbalance between production of free radicals and the system’s ability to readily detoxify reactive intermediates. This event consequently causes DNA damage, lipid peroxidation, protein modification, and possibly symptomatic effects for various diseases including cancer. This review discusses predominant modes of action and numerous molecular markers. Attention is paid to metal-induced generation of free radicals, the phenomenon of oxidative stress, damage to DNA, lipid, and proteins, responsive signal transduction pathways with major roles in cell growth and development, and roles of antioxidant enzymatic and DNA repair systems. Interaction of non-enzymatic antioxidants (carotenoids, flavonoids, glutathione, selenium, vitamin C, vitamin E, and others) with cellular oxidative stress markers (catalase, glutathione peroxidase, and superoxide dismutase) as well as certain regulatory factors, including AP-1, NF-κB, Ref-1, and p53 is also reviewed. Dysregulation of protective pathways, including cellular antioxidant network against free radicals as well as DNA repair deficiency is related to oncogenic stimulation. These observations provide evidence that emerging oxidative stress-responsive regulatory factors and DNA repair proteins are putative predictive factors for tumor initiation and progression

Mesure des sections efficaces de diffusion élastique des neutrons sur le carbone et le fluor dans le domaine épithermique sur la plate-forme PEREN

Le Réacteur à Sels Fondus (RSF) en cycle Th/U est un des concepts de nouvelle génération pour la production d'énergie nucléaire. Un RSF type se compose d'une structure en graphite, servant de modérateur, percé de canaux dans lesquels circule le sel fondu (7LiF+ThF4+UF4). Les données neutroniques fondamentales pour les simulations numériques sont les sections efficaces de diffusion élastique d'un neutron sur des noyaux de carbone ( C), de fluor ( F) et de lithium 7 ( Li) dans le domaine épithermique. Le but de ce travail est de de terminer précisément C et F entre 1 eV et 100 keV. Ces mesures ont été réalisées auprès de la plate-forme d'Etude et de Recherche sur l'Electro-Nucléaire (PEREN) du Laboratoire de Physique Subatomique et de Cosmologie de Grenoble. Elle comprend un GEnérateur de NEutrons Pulsé Intense (GENEPI) produisant des neutrons de 2.5 MeV au centre de massifs ralentisseurs (C et CF2). Des taux de capture sont obtenus, pour des échantillons composés de matériaux de référence (Au, Ag, Mo et In) placés dans les massifs, à l'aide d'un scintillateur YAP couplé à un photo-multiplicateur. Des simulations précises des expériences, avec le code MCNP, ont été réalisées et la comparaison entre la simulation et l'expérience a permis de déterminer C et F avec des précisions de 1% et 2% respectivement, mettant en évidence des écarts avec les données nucléaires évaluées (ENDF). Des mesures complémentaires des sections efficaces totales C et F à plus haute énergie (200 - 600keV) ont été effectuées au Centre d'Etudes Nucléaires de Bordeaux par une méthode de transmission. Un faisceau de neutrons mono-énergétique est produit par des protons accélérés, dans un accélérateur Van De Graaff, sur une cible de LiF. Les neutrons transmis sont comptés par un détecteur proportionnel à hydrogène. Des écarts de 5% (C) et de 9% (F) par rapport à ENDF ont été mis en évidence.GRENOBLE1-BU Sciences (384212103) / SudocSTRASBOURG-Bib.Central Recherche (674822133) / SudocSudocFranceF

Cycles uranium et thorium en réacteurs à neutrons rapides refroidis au sodium (Aspects neutroniques et déchets associés)

Les réacteurs à neutrons rapides refroidis au sodium à cycle uranium 238/plutonium 239, dont la faisabilité technique a déjà été éprouvée, permettent de s'affranchir du problème des ressources d'uranium naturel en réalisant la régénération de l'élément fissile du combustible. En outre, une gestion des déchets visant à réduire la production et la radiotoxicité des actinides mineurs produits par le réacteur peut être mise en œuvre en transmutant les AM en cœur (transmutation homogène). Une autre alternative pour minimiser les déchets est l'utilisation d'un autre couple fertile-fissile: le thorium 232 et l'uranium 233 (Th/U). La comparaison des deux cycles est menée sur les aspects neutroniques et la sûreté et sur la production de déchets, en utilisant un Monte Carlo évoluant. Concernant la radiotoxicité des déchets, même si on ne dégage pas véritablement d'avantages clairs pour un cycle ou l'autre, le cycle Th/U réduit la radiotoxicité durant les périodes où elle est la plus élevée. La transmutation homogène réduit significativement, pour les deux cycles, la radiotoxicité des déchets, de facteurs variables selon la période de temps considéré. Toutefois, elle se fait au détriment d'une augmentation importante de l'inventaire des AM dans le cœur. Si l'on considère la fin de jeu, l'inventaire du cœur du réacteur devient alors un déchet. Le gain apporté par la transmutation, en prenant en compte à la fois la radiotoxicité du cœur et des déchets cumulés, sera quantifié, et montre que la transmutation n'offre pas de gain considérable si l'incinération des éléments fissiles rinci aux Pu ou U selon le c cie n'est as mise en œuvre lors de l'arrêt de la filière.Sodium fast reactors (SFR-Na) with uranium 238/plutonium 239(U/Pu) cycle, its technical feasibility has already proven, allow to overcome the problem ofnatural uranium resources in achieving the regeneration of the fuel fissile element. ln addition, a waste management can be performed to reduce the radiotoxicity of actinides produced by the reactor in transmuting the AM in the core (homogeneous transmutation). Another alternative to minimize waste is to use another couple fertile-fissile: the thorium 232 and the uranium 233 (Th/U). The comparison is performed on neutronic and safety aspects and on waste production, in using an evolving Monte Carlo. Although one does not disclose real clear advantages concerning the radiotoxicity ofwastes for a particular cycle, the Th/U cycle reduces the radiotoxicity during periods when it is the highest. The homogeneous transmutation minimizes significantly for both cycles, radiotoxicity ofwastes, with different factors depending on the considered time period. However, it is done to the detriment of an important increase of AM in the core. lfwe consider the nuclear stop, the inventory of the reactor core becomes a waste. The gain provided by the transmutation, taking into account both the core and accumulated waste radiotoxicities, will be quantified, and shows the transmutation does not provide a significant gain if the buming of main fissile elements is not considered when the nuclear is stopped.ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF

Angular momentum of doubly magic ¹³²Sn fission product: Experimental and theoretical aspects

International audienceDespite the numerous theoretical and experimental works published very recently, the way in which fission fragments acquire their angular momentum is still an open question. This angular momentum generation mechanism is important not only for improving our understanding of the fission process, but also for nuclear energy applications, since the angular momentum of fission fragments strongly impact the prompt gamma spectra and consequently the decay heat in a reactor. In this context, within the framework of a collaboration between the ‘Laboratoire de Physique Subatomique et Corpusculaire’ (LPSC, France), the ‘Institut Laue Langevin’ (ILL, France) and the CEA-Cadarache (France), an experimental program was developed on the LO-HENGRIN mass-spectrometer with the aim of measuring isomeric ratio of some fission products for different thermal-neutron-induced fission reactions. This paper will be focused on the results obtained for the spherical nucleus 132Sn following thermal-neutron-induced fission of both 235U and 241Pu targets. To further challenge the angular momentum generation models, 132Sn isomeric ratio (IR) was measured as a function of 132Sn fission product kinetic energy (KE). The angular momentum was determined by combining our experimental data with the calculations performed with the FIFRELIN Monte Carlo code. A clear angular momentum decrease with KE was observed for both reactions. Lastly, we investigate the dependence of the 132Sn angular momentum with the incident neutron energy, from thermal region up to 5 MeV (below the second-chance fission). For that, the four free available parameters in FIFRELIN are selected in order to reproduce the average prompt neutron multiplicity. In this way, the angular momentum is deduced for each neutron energy. These results are discussed in terms of the impact of the available intrinsic excitation energy at scission on the spin generation mechanism.</jats:p

Automated selection of nuclides and reactions of interest in a depletion simulation. Precision loss estimation for multiple outputs

International audienceTo accelerate depletion calculations, it is common to only consider a selection of isotopes. Simulating only a limited number of nuclides leads inevitably to some bias on the outputs of the depletion simulation. Most methods used are either implicit or dedicated to specific cases. This paper presents a new method, based on physics consideration and an explicit algorithm, that automatically selects isotopes and reactions for a depletion calculation. This method uses the creation and simplification of a nucleus tree gathering and linking together all nuclides that can possibly be created during the depletion process. This is performed by recursively adding nuclides possibly created from nuclides previously in the tree through decay or nuclear reaction. After the creation of the tree, it can be simplified by automatically cutting nuclides and reaction out through 3 processes: half-life threshold, cross-section threshold and reaction type cut. Using these simplification processes, the presented method leads to important calculation cost reduction (up to 40%) with effect on outputs lower than 3 times their stochastic standard deviation

New measurements on isobaric fission product yields and mean kinetic energy for 241Pu thermal neutron-induced fission

Nuclear fission yields data measurements for thermal neutron induced fission of 241Pu have been carried out at the Institut Laue Langevin (ILL) in Grenoble, using the Lohengrin mass spectrometer. Mass, isotopic and isomeric yields have been extracted for the last measurements. A focus is given in this document to the mass yield results which are obtained for almost the entire heavy peak and most of the light high yields masses, along with the covariance matrix. The mean kinetic energy as a function of the fission product mass has also been extracted from the measurements. The total mean kinetic energy pre and post neutron emission have been assessed and compared to other works showing a rather good agreement

New measurements on isobaric fission product yields and mean kinetic energy for

Nuclear fission yields data measurements for thermal neutron induced fission of 241Pu have been carried out at the Institut Laue Langevin (ILL) in Grenoble, using the Lohengrin mass spectrometer. Mass, isotopic and isomeric yields have been extracted for the last measurements. A focus is given in this document to the mass yield results which are obtained for almost the entire heavy peak and most of the light high yields masses, along with the covariance matrix. The mean kinetic energy as a function of the fission product mass has also been extracted from the measurements. The total mean kinetic energy pre and post neutron emission have been assessed and compared to other works showing a rather good agreement