Images du quotidien et patrimoines sociaux : la mise en images d’archives

L’objet du chapitre est de faire émerger des éléments de convergence quant aux étapes de la mise en images d’archives. D’abord, la conservation. Que l’on se situe dans une dialectique du passé à travers des images anciennes ou que l’on ait affaire au désir de transmission d’images récentes, l’impératif de la pérennisation joue et l’injonction des archives est à l’œuvre. Ensuite, la monstration. Que l’image originelle soit intégrée au décor d’un restaurant ou partagée dans une communauté virtuelle, il n’est guère d’image d’archives que vue et offerte au regard. Le statut d’image d’archives est conféré par un regard extérieur, en dehors du cercle de production et de diffusion initial – la famille par exemple. Enfin, la modification. L’image d’archives ne se conçoit que médiatisée, insérée dans un discours et presque toujours modifiée : découpée, agrandie, teintée, détournée de son objet initial, décryptée, c’est véritablement une autre image qui est produite à partir de l’image primaire. L\u27image créée et mise en scène joue sur des codes convenus, dans une allusion explicite ou plus discrète, à ceux des patrimoines savants. Les procédés de médiation co-construisent l\u27image d\u27archives parce qu\u27ils la mettent en exposition et ainsi déclenchent son accréditation comme objet patrimonial. Le statut d\u27image d\u27archives ne serait donc que transitoire, valable uniquement au moment et dans l’instant de son usage, contrairement à celui de document d’archives ou d’image archivée, défini par un lieu de conservation fixe et des modalités d’accès stables

Images archivées, images d’archives : fortunes terminologiques

On ne peut manquer d’être frappé de la quasi-totale absence dans l’institution archivistique française et dans les milieux professionnels qui l’animent, du moins jusqu’à une date récente, non seulement de l’expression « image d’archives » mais encore du mot même « image ». Cette constatation constitue le point de départ d’une enquête terminologique et lexicologique : d’où vient cette expression « images d’archives » ? Quelles sont les étapes et les raisons de sa diffusion 

Natural Nuclear Reactor Oklo and Variation of Fundamental Constants Part 1: Computation of Neutronics of Fresh Core

Using modern methods of reactor physics we have performed full-scale calculations of the natural reactor Oklo. For reliability we have used recent version of two Monte Carlo codes: Russian code MCU REA and world wide known code MCNP (USA). Both codes produce similar results. We have constructed a computer model of the reactor Oklo zone RZ2 which takes into account all details of design and composition. The calculations were performed for three fresh cores with different uranium contents. Multiplication factors, reactivities and neutron fluxes were calculated. We have estimated also the temperature and void effects for the fresh core. As would be expected, we have found for the fresh core a significant difference between reactor and Maxwell spectra, which was used before for averaging cross sections in the Oklo reactor. The averaged cross section of Sm-149 and its dependence on the shift of resonance position (due to variation of fundamental constants) are significantly different from previous results. Contrary to results of some previous papers we find no evidence for the change of the fine structure constant in the past and obtain new, most accurate limits on its variation with time: -4 10^{-17}year^{-1} < d alpha/dt/alpha < 3 10^{-17} year^{-1} A further improvement in the accuracy of the limits can be achieved by taking account of the core burnup. These calculations are in progress.Comment: 25 pages, 14 figures, 12 tables, minor corrections, typos correcte

Porewater methane transport within the gas vesicles of diurnally migrating Chaoborus spp.: An energetic advantage

We show that diurnally migrating Chaoborus sp. (phantom midge larvae), which can be highly abundant in eutrophic lakes with anoxic bottom, utilises sediment methane to inflate their tracheal sacs, which provides positive buoyancy to aid vertical migration. This process also effectively transports sediment methane bypassing oxidation to the upper water column, adding to the total methane outflux to the atmosphere

Dementia diagnostics in primary care : a representative 8-year follow-up study in Lower Saxony, Germany

AIM: To investigate whether primary-care physicians' competency regarding dementia diagnostics improved from 1993 to 2001. METHODS: In a representative follow-up survey 122 out of 170 (71.8%) family physicians (FPs) were randomly assigned to 2 written case samples presenting patients with slight memory impairment (case 1a: female vs. case 1b: male) and moderate dementia [vascular type (case 2a) vs. Alzheimer's disease (case 2b)]. Potential diagnostic workup was inquired by a structured face-to-face interview. RESULTS: 'Basic' diagnostics like history taking or laboratory investigations were considered in the first place. In case 1, neuropsychological screening was significantly more frequently considered at follow-up (19.3% in 1993 vs. 31.1% in 2001); it still would have been applied rarely in case 2 (2a: 14.1 vs. 14.8%; 2b: 23.5 vs. 24.6%). Neuroimaging remained not to be considered as a standard procedure, and only a minority of FPs would have performed a screening for depression (2001: 1a: 6.7%; 1b: 11.3%; 2a: 0.0%; 2b: 1.6%). CONCLUSIONS: With regard to dementia diagnostics in primary care, guideline adherence remained low at follow-up. Structured training efforts aiming at FPs appear to be necessary

Pitfalls in uncertainty estimation : few measurements, non-gaussian distributions

In metrology practice, uncertainty budget calculation might include components based on little measurements data. The concept of coverage factor at a given level of confidence to combined uncertainty is taking care of this lack of information. We propose to apply a similar factor to the individual component(s) of an uncertainty budget when the value is calculated with limited number of measurements. These factors have the same function as the coverage factor defined in the GUM but on the level of the individual component of the total uncertainty. The goal of the work is to provide values of these factors for practical use. Inspired from the Supplement 1 of the GUM, we use Monte Carlo simulations to calculate the component coverage factors for repeated measurements from non-normal distributions. We apply the algorithm to the most common distributions in metrology, for 95% and 99% confidence level: rectangular, arc sine, triangular and trapezoidal distributions

Damage identification using modal data: Experiences on a prestressed concrete bridge

Large scale tests with progressive damage on a prestressed concrete highway bridge have been performed to investigate the sensitivity of several damage detection, localization, and quantification methods based on modal parameters. To investigate the quality of modal parameters, the data set of one damage step was analyzed by several output-only identification techniques. Although the bridge was severely cracked, natural frequencies as well as mode shapes display only minor changes. However, the relative changes of mode shapes are larger than those observed for natural frequencies. A novel damage indicator, called mode shape area index, based on changes of mode shapes, has been developed and found as the most sensitive damage detection approach. Damage detection or localization via changes of the flexibility matrix performed better than natural frequencies or mode shapes alone. The application of the direct stiffness calculation and a sensitivity-based model update technique showed results having a high level of ambiguity about the location and quantification of damage also at the highest damage level. Evaluating the information collected in this study the test results indicate that an early stage damage identification in prestressed concrete bridges is hardly possible because of the nearly complete recovery of stiffness after closing of cracks in prestressed concrete and the effect of environmental parameters on modal data