425 research outputs found
Allocating and Funding Universal Service Obligations in a Competitive Network Market
We examine, in a network market open to competition, various mechanisms of allocating and funding ''universal service obligations'' among agents (rival operators and consumers). The obligations we consider are geographic ubiquity and non discrimination. We analyze, from both the efficiency and equity point of views, the respective advantages of a ''restricted-entry'' system (where the entrant is not allowed to serve high cost consumers) and the ''pay or play'' system at work for instance in Australia. We show that the pay or play regulation always dominates the restricted-entry regulation under ubiquity constraint alone. This result no longer holds when the regulator imposes also the non discrimination constraint.
Autonomie, l'apprentissage informel de l'anglais en ligne et les centres de ressources en langues (CRL): Les liens entre l'autonomie de l'apprenant, la compétence en L2, l'autonomie en L2 et la litératie numérique
International audienceLearners' varied Web 2.0 and informal online learning practices and subsequent language acquisition would appear to have multiple and complex links to autonomy, affecting L2 autonomy, learner autonomy and general autonomy. If we consider language learning through the lens of complex dynamic systems theory (CDST; Larsen-Freeman & Cameron 2007, De Bot, Lowie & Verspoor 2007), autonomy (of various types) and L2 proficiency and digital literacy would all seem to be acting as attractor states (Hiver, 2015), creating movements potentially leading to virtuous or vicious circles in consecutive feedback loops. Drawing on examples from the online informal learning of English (OILE) such as watching foreign language series, participating in online forums and multi-player online gaming, we attempt to provide a complex dynamic systems analysis of the autonomy and proficiency interactions at play in these types of learning situations
Risk factors for reperfusion injury after lung transplantation
Objective: To assess the influence of recipient's and donor's factors as well as surgical events on the occurrence of reperfusion injury after lung transplantation. Design and setting: Retrospective study in the surgical intensive care unit (ICU) of auniversity hospital. Methods: We collected data on 60 lung transplantation donor/recipient pairs from June1993 to May2001, and compared the demographic, peri- and postoperative variables of patients who experienced reperfusion injury (35%) and those who did not. Results: The occurrence of high systolic pulmonary pressure immediately after transplantation and/or its persistence during the first 48 h after surgery was associated with reperfusion injury, independently of preoperative values. Reperfusion injury was associated with difficult hemostasis during transplantation (p = 0.03). Patients with reperfusion injury were more likely to require the administration of catecholamine during the first 48 h after surgery (p = 0.014). The extubation was delayed (p = 0.03) and the relative odds of ICU mortality were significantly greater (OR 4.8, 95% CI: 1.06, 21.8) in patients with reperfusion injury. Our analysis confirmed that preexisting pulmonary hypertension increased the incidence of reperfusion injury (p < 0.01). Conclusions: Difficulties in perioperative hemostasis were associated with reperfusion injury. Occurrence of reperfusion injury was associated with postoperative systolic pulmonary hypertension, longer mechanical ventilation and higher mortality. Whether early recognition and treatment of pulmonary hypertension during transplantation can prevent the occurrence of reperfusion injury needs to be investigate
Isotopic distribution of fission fragments in collisions between 238U beam and 9Be and 12C targets at 24 MeV/u
Inverse kinematics coupled to a high-resolution spectrometer is used to
investigate the isotopic yields of fission fragments produced in reactions
between a 238U beam at 24 MeV/u and 9Be and 12C targets. Mass, atomic number
and isotopic distributions are reported for the two reactions. These
informations give access to the neutron excess and the isotopic distribution
widths, which together with the atomic-number and mass distributions are used
to investigate the fusion-fission dynamics.Comment: Submitted to PR
New pathway to bypass the 15O waiting point
We propose the sequential reaction process
O(,)O as a new pathway to bypass of the
O waiting point. This exotic reaction is found to have a surprisingly
high cross section, approximately 10 times higher than the
O(,)O. These cross sections were calculated after
precise measurements of energies and widths of the proton-unbound F low
lying states, obtained using the H(O,p)O reaction. The large
cross section can be understood to arise from the more
efficient feeding of the low energy wing of the ground state resonance by the
gamma decay. The implications of the new reaction in novae explosions and X-ray
bursts are discussed.Comment: submitte
Probing Nuclear forces beyond the drip-line using the mirror nuclei N and F
Radioactive beams of O and O were used to populate the resonant
states 1/2, 5/2 and in the unbound F and F
nuclei respectively by means of proton elastic scattering reactions in inverse
kinematics. Based on their large proton spectroscopic factor values, the
resonant states in F can be viewed as a core of O plus a proton
in the 2s or 1d shell and a neutron in 1p. Experimental
energies were used to derive the strength of the 2s-1p and
1d-1p proton-neutron interactions. It is found that the former
changes by 40% compared with the mirror nucleus N, and the second by
10%. This apparent symmetry breaking of the nuclear force between mirror nuclei
finds explanation in the role of the large coupling to the continuum for the
states built on an proton configuration.Comment: 6 pages, 3 figures, 2 tables, accepted for publication as a regular
article in Physical Review
Spectroscopy of Na: Bridging the two-proton radioactivity of Mg
The unbound nucleus Na, the intermediate nucleus in the two-proton
radioactivity of Mg, was studied by the measurement of the resonant
elastic scattering reaction Ne(p,Ne)p performed at 4 A.MeV.
Spectroscopic properties of the low-lying states were obtained in a R-matrix
analysis of the excitation function. Using these new results, we show that the
lifetime of the Mg radioactivity can be understood assuming a sequential
emission of two protons via low energy tails of Na resonances
Production of neutron-rich fragments with neutron number N > Nprojectile in the reaction Ca (60 MeV/nucleon) + Ta
Expérience GANIL, Spectrometre LISEInternational audienceThe goal of the present paper is to attempt to clarify the nuclear reaction mechanism leading to the production of fragments at zero degree with neutron number larger than that in the 48Ca projectile, at about 60 MeV per nucleon. The production cross sections of the extremely neutron-rich Si and P isotopes were measured. Concerning the nuclear reaction mechanism leading to the production of these isotopes, one should probably refer to a particular type of transfer mechanism, which results in low excitation energy for the fragments, rather than to the ‘genuine' fragmentation mechanism. An upper limit of about 0.05 pb was estimated for the production cross section for the 47P isotope for which no count was observed
Spatio-temporal permanence and plasticity of foraging trails in young and mature leaf-cutting ant colonies (Atta spp.)
The distribution and formation of foraging trails have largely been neglected as factors explaining harvesting
patterns of leaf-cutting ants.We applied fractal analysis, circular, and conventional statistics to published and newly
recorded trailmaps of seven Atta colonies focusing on three aspects: permanence, spatio-temporal plasticity and colony
life stage. In the long term, trail patterns of young and mature Atta colonies revealed that foraging activities were
focused on distinct, static sectors that made up only parts of their potentially available foraging range. Within these
foraging sectors, trails were typically ephemeral and highly variable in space and time. These ephemeral trails were
concentrated around permanent trunk trails in mature and around nest entrances in young colonies. Besides these
similarities, the comparison of trail systems between the two life stages indicated that young colonies exploited fewer
leaf sources, used smaller and less-complex systems of foraging trails, preferred different life forms as host plants, and
switched hosts more often compared with mature colonies. Based on these analyses, we propose a general hypothesis
which describes the foraging pattern in Atta as a result of initial foraging experiences, spatio-temporal distribution of
suitable host plants, energetic constraints, and other factors such as seasonality and interspecific predatio
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