During the last years, several Cm and Cf isotopes have been studied by our research group in the frame of a systematic investigation of gas emission characteristics in ternary fission. Here we report on new results on the energy distribution and the emission probability of 3H, 4He and He particles emitted in the spontaneous ternary fission of 250Cf (Eexc = 0 MeV) and in the neutron induced ternary fission of 249Cf (Eexc = 6.625 MeV). Both measurements were performed using suited and well-calibrated Δ E-E telescope detectors, at the IRMM (Geel, Belgium) for the spontaneous fission and at the very intense neutron beam PF1b at the Institute Laue-Langevin (Grenoble, France) for the neutron induced fission measurement. In this way, the existing database can be enlarged with new results for Z = 98 isotopes, which is important for the systematic investigation. Moreover, the investigation of the `isotope couple' 249Cf(n,f)-250Cf(SF), together with corresponding data for other isotopes, will yield valuable information on the influence of the excitation energy on the particle emission probabilities
International audienceThe even-odd staggering observed in the experimental fission-fragment nuclear-charge yields is investigated over a wide systematics of fission fragments measured at Lohengrin in direct kinematics and at GSI in inverse kinematics. The general increase of the even-odd staggering in the fission-fragment charge yields towards asymmetric charge splits is explained by the absorption of the unpaired nucleons by the heavy fragment. As a consequence, the well established trend of evenodd staggering in the fission fragment charge yields to decrease with the fissility is attributed in part to the asymmetry evolution of the charge distribution. This interpretation is strongly supported by the data measured at GSI, which cover the complete charge distribution and include precise yields at symmetry. They reveal that the even-odd effect around symmetry remains constant over a large range of fissility
Over the last five years, new evaluations of plutonium and uranium have been performed at Bruyeres‐le‐Châtel from the resolved resonance region up to 30 MeV. Only nuclear reactions models have been used to build these evaluations. Total, shape elastic and direct inelastic cross sections are obtained from a coupled channel model using a dispersive optical potential devoted to actinides. All the other cross sections are calculated owing to the Hauser‐Fesbach theory. We take particular care over the fission channel. For uranium isotopes, a triple‐humped barrier is required in order to reproduce accurately the variations of the experimental fission cross sections. As not commonly expected, we show that the effect of the class II or class III states located in the wells of the aforementioned fission barrier provide sometimes an anti‐resonant transmission rather than a resonant. With increasing neutron incident energy, a lot of residual nuclei produced by nucleon emission lead to fission also. All available exp...
We present a theoretical model of residential growth that emphasises the path-dependent nature of urban sprawl patterns. The model is founded on the monocentric urban economic model and uses a cellular automata (CA) approach to introduce endogenous neighbourhood effects. Households are assumed both to like and to dislike the density of their neighbourhood, and are assumed to trade-off this density with housing space consumption and commuting costs. Discontinuous spatial patterns emerge from that trade-off, with the size of suburban clusters varying with time and distance to the centre. We use space-time diagrams inspired from 1D elementary CA to visualise changes in spatial patterns through time and space, and undertake sensitivity analyses to show how the pattern and timing of sprawl are affected by neighbourhood preferences, income level, commuting costs, or by imposing a green belt
Obesity is associated with increased risk for developing pancreatic cancer, and it is suggested that insulin resistance provides the missing link. Here we demonstrate that under the context of genetic susceptibility, a high fat diet (HFD) predisposes mice with oncogenicK-ras activation to accelerated pancreatic intraepithelial neoplasm (PanIN) development. Tumor promotion is closely associated with increased inflammation and abrogation of TNFR1 signaling significantly blocks this process underlining a central role for TNFα in obesity-mediated enhancement of PanIN lesions. Interestingly, however, despite increased TNFα levels, mice remain insulin sensitive. We show that, while aggravating tumor promotion, a HFD exerts dramatic changes in energy metabolism through enhancement of pancreatic exocrine insufficiency, metabolic rates, and expression of genes involved in mitochondrial fatty acid (FA) β-oxidation that collectively contribute to improved glucose tolerance in these mice. While on one hand these findings provide significant evidence that obesity is linked to tumor promotion in the pancreas, on the other it suggests alterations in inflammatory responses and bioenergetic pathways as the potential underlying cause.
Two forms of a plant-specific RNA polymerase (Pol), PolIV(PolIVa) and PolV(PolIVb), currently defined by their respective largest subunits [NRPD1(NRPD1a) and NRPE1(NRPD1b)], have been implicated in the production and activity of 24-nt small RNAs (sRNAs) in RNA-directed DNA methylation (RdDM). Prevailing models support the view that PolIV(PolIVa) plays an upstream role in RdDM by producing the 24-nt sRNAs, whereas PolV(PolIVb) would act downstream at a structural rather than an enzymatic level to reinforce sRNA production by PolIV(PolIVa) and mediate DNA methylation. However, the composition and mechanism of action of PolIV(PolIVa)/PolV(PolIVb) remain unclear. In this work, we have identified a plant-specific PolV(PolIVb) subunit, NRPE5a, homologous to NRPB5a, a common subunit shared by PolI-III and shown here to be present in PolIV(PolIVa). Our results confirm the combinatorial diversity of PolIV(PolIVa)/PolV(PolIVb) subunit composition and indicate that these plant-specific Pols are eukaryotic-type polymerases. Moreover, we show that nrpe5a-1 mutation differentially impacts sRNAs accumulation at various PolIV(PolIVa)/PolV(PolIVb)-dependent loci, indicating a target-specific requirement for NRPE5a in the process of PolV(PolIVb)-dependent gene silencing. We then describe that the triad aspartate motif present in the catalytic center of PolV(PolIVb) is required for recapitulation of all activities associated with this Pol complex in RdDM, suggesting that RNA polymerization is important for PolV(PolIVb) to perform its regulatory functions.
Bardet-Biedl syndrome (BBS) is an inherited ciliopathy generally associated with severe obesity, but the underlying mechanism remains hypothetical and is generally proposed to be of neuroendocrine origin. In this study, we show that while the proliferating preadipocytes or mature adipocytes are nonciliated in culture, a typical primary cilium is present in differentiating preadipocytes. This transient cilium carries receptors for Wnt and Hedgehog pathways, linking this organelle to previously described regulatory pathways of adipogenesis. We also show that the BBS10 and BBS12 proteins are located within the basal body of this primary cilium and inhibition of their expression impairs ciliogenesis, activates the glycogen synthase kinase 3 pathway, and induces peroxisome proliferator-activated receptor nuclear accumulation, hence favoring adipogenesis. Moreover, adipocytes derived from BBS-patients' dermal fibroblasts in culture exhibit higher propensity for fat accumulation when compared to controls. This strongly suggests that a peripheral primary dysfunction of adipogenesis participates to the pathogenesis of obesity in BBS.
A major involvement of IFNalpha in the etiopathogenesis of systemic lupus erythematosus has been suggested by clinical observations, including the increase of serum levels of this cytokine in patients with active disease. Supporting this hypothesis, we have shown that expression of IFNalpha from a recombinant adenovirus (IFNalpha Adv) precipitates lupus manifestations in genetically susceptible New Zealand Black (NZB) x New Zealand White (NZW)F(1) mice (NZB/W) but not in BALB/c mice. In the present investigation, we have prepared an IFNalpha immunogen, termed IFNalpha kinoid, which, appropriately adjuvanted, induces transient neutralizing antibodies (Abs) but no cellular immune response to the cytokine and without apparent side effects. Using this preparation, we also showed that, in kinoid-vaccinated NZB/W mice, lupus manifestations, including proteinuria, histological renal lesions, and death triggered by IFNalpha Adv challenge were delayed/prevented as long as an effective threshold of anti-IFNalpha inhibitory capacity was present in the serum.