Internal conversion and summing effects in heavy-nuclei spectroscopy

Expérience GANIL, spectrometre LISEInternal conversion of low-energy nuclear transitions occurs with a high probability in heavy nuclei. After the emission of the conversion electron, a cascade of X-rays, Auger or Coster–Krönig electrons takes place. In $\alpha$-decay experiments in which the nuclei of interest are implanted into a silicon detector, these atomic processes contribute to the detected energy. To understand the distortions of $\alpha$-particle energy spectra, knowledge of the various atomic yields is required. Using state-of-the-art calculations, new atomic yields are computed in $_99$Es and compared to those available in the literature. Detailed simulations of the $^{251}_{101}$Md $\alpha$ decay are performed and compared to experimental data. Possible ways to discriminate between the available atomic yields are also discussed

Disconnection, network dysfunction and cognitive impairment after traumatic brain injury

It is now widely accepted that cognitive functions depend on the integrated operation of large-scale distributed brain networks. Recent methodological advances allow both structural and functional connectivity within these networks to be studied non-invasively in vivo. These approaches hold the promise of dramatically extending our understanding of the impact of traumatic brain injury (TBI) on cognition, which should help determine strategic targets for the rehabilitation of individuals with TBI. In this thesis, I present three studies that combine structural and functional magnetic resonance imaging to test the general hypothesis that cognitive deficits after TBI arise from structural disconnection within brain networks that mediate cognitive functions. In the first study, I demonstrate that sustained attention deficits in TBI patients are related to a failure to regulate activity within a ‘default-mode’ network (DMN) thought to be involved, among others, in internally directed processes such as self-referential thought. In addition, these deficits can be predicted by the functional and structural connectivity within the DMN. Next, I present a study investigating the neural basis for inhibitory control in healthy subjects using a modified version of the Stop Signal Task (SST). This study allows a clear distinction between attentional and response inhibition processes, and paves the way for my last study, which investigates inhibitory deficits after TBI. In this study, I demonstrate that a failure of DMN deactivation during response inhibition is associated with impaired inhibitory performance in TBI patients. The ability to efficiently regulate the DMN can be predicted by the structural integrity within a remote brain network previously proposed to be involved in switching between internally and externally directed attention. This work identifies DMN dysfunction as underlying various cognitive deficits after TBI, and confirms the relevance of white matter damage in the development of brain dysfunctions after TBI

Newspaper Treatment of the Viking Mission to Mars, 1975-76

The study's problem was whether five major newspapers that covered Viking produced informative, educational, interpretive, and credible stories. Indexed, microfilmed articles from January, 1975, to November, 1976, were analyzed. Conclusions: no newspaper gave the landings the greatest percentage of coverage; every newspaper devoted the largest percentage of coverage to interpretation; science writers used analogy most often; adequate explanations of Viking's implications were not found; four of five newspapers had more references to named than unnamed sources; only two newspapers utilized their staffs more than outside sources. Recommendations: covering a science event should be planned to include preliminary coverage, follow-up, and analysis; writers must interpret the facts, use educational writing techniques, explain implications, and have specific attribution; newspapers should assess their capabilities for science coverage

Protection of stainless-steels against corrosion in sulphidizing environments by Ce oxide coatings: X-ray absorption and thermogravimetric studies

In this paper a study is reported concerning ceramic coatings containing cerium oxide, prepared by the sol-gel method, used to protect Incoloy 800H against sulphidation. When the coating is sintered in air at 850°C good protection is obtained. In an X-ray absorption spectroscopic study of the coatings it was observed that the best protective coating contains all cerium as CeIV after pretreatment. After sulphidizing cerium was reduced to CeIII. Possible mechanisms to explain the protective properties are discussed

Cauchois and S\'en\'emaud Tables of wavelengths of X-ray emission lines and absorption edges

We present the Cauchois and S\'en\'emaud Tables of X-ray emission lines and absorption edges. They are written both in French and English. They were published in 1978 by Pergamon Press and are insufficiently known. However they are of large interest because of their completeness. They comprise the energies of all the K, L, M, N and O emission lines of natural elements from lithium up to uranium as well as the energies of satellite emissions and absorption discontinuities. The more intense lines of radio-elements up to fermium (Z = 100) are also given. The Tables range from the hard X-rays (122 keV, 0.01 nm) to the extreme ultra-violet (12 eV, 102 nm). For each transition, the wavelength ({\AA} and uX) and energy (eV and Ry) are given and references are indicated. The transitions are grouped by increasing wavelength (decreasing photon energy) and also by element and spectral series. We present, as an example, the use of the Tables to identify the emissions of the molybdenum L spectrum. We decided to scan the Cauchois and S\'en\'emaud Tables and make them available for the scientific community. They are now available at the Website of our laboratory, http://www.lcpmr.upmc.fr/.Comment: The Cauchois and S\'en\'emaud Tables are now available at the following address : http://www.lcpmr.upmc.fr/themes-A2f.php The definitive version of the paper is available at www3.interscience.wiley.com X-Ray Spectrom. 2011, 40, 12-1

Characterization of reward and effort mechanisms in apathy

AbstractApathy is a common but poorly understood condition with a wide societal impact observed in several brain disorders as well as, to some extent, in the normal population. Hence the need for better characterization of the underlying mechanisms. The processes by which individuals decide to attribute physical effort to obtain rewards might be particularly relevant to relate to apathy traits. Here, we designed two paradigms to assess individual differences in physical effort production and effort-based decision-making and their relation to apathy in healthy people. Apathy scores were measured using a modified version of the Lille Apathy Rating Scale, suitable for use in a non-clinical population.In the first study, apathy scores were correlated with the degree to which stake (reward on offer) and difficulty level impacts on physical effort production. Individuals with relatively high apathy traits showed an increased modulation of effort while more motivated individuals generally exerted greater force across different levels of stake. To clarify the underlying mechanisms for this behavior, we designed a second task that allows independent titration of stake and effort levels for which subjects are willing to engage in an effortful response to obtain a reward. Our results suggest that apathy traits in the normal population are related to the way reward subjectively affects the estimation of effort costs, and more particularly manifest as decreased willingness to exert effort when rewards are small, or below threshold. The tasks we introduce here may provide useful tools to further investigate apathy in clinical populations

Psychedelics as potential catalysts of scientific creativity and insight

Creativity, that is the creation of ideas or objects considered both novel and valuable, is among the most important and highly valued of human traits, and a fundamental aspect of the sciences. Dreams and hypnagogic states have been highly influential in promoting scientific creativity and insight, contributing to some important scientific breakthroughs. Phenomenologically, the latter states of consciousness share a great deal of overlap with the psychedelic state, which has also been associated with facilitating scientific creativity on occasion. The current article proposes that the dream, hypnagogic and psychedelic states share common features that make them conducive to supporting some aspects of scientific creativity and examines the putative underlying neurophenomenological and cognitive processes involved. In addition, some notable occurrences of scientific insights that have emerged from these types of altered states are reviewed and shared common features are presented, providing a ground for future research. The psychedelic state may have its own characteristic features making it amenable to creativity enhancement, such as brain hyperconnectivity, meta-cognitive awareness, access to a more dependable and sustained altered state experience, and potential for eliciting sustained shifts in trait openness. The contextual factors which may contribute to enhancement of scientific creativity and insight will be evaluated. While research in this area is limited, further work to elucidate how psychedelics may best contribute to scientific creativity enhancement is warranted