Statistical distribution of time values and underestimation of the benefits of speed

International audienceHighlights : • Users' time savings are important in calculating net present value of a transport project.• The monetary estimates of time savings depend on the value of the time used.• The official methods of calculation most often use average values.• Using the statistical distribution of the values of time substantially modifies the result.• The higher the cost of transportation, the greater the underestimation of user surpluses.</br

Modèles de trafic et évaluation des avantages dans le calcul économique

International audienceTransport infrastructure projects are based on ex ante cost benefit analysis. Traveler surplus often represent a large part of a project’s global benefit. The assessment of these traveler benefits, or surplus, as recommended in official French guidelines, is based on average benefits for a project. But in fact, benefits are widely distributed among individual travelers and discreet choice models enable us to have access to this distribution. The aim of this paper is to show that using the surplus given by discreet choice models leads to higher amounts of benefits compared to “classical” methods when the project has a high cost for users. The example of tolled highways is simulated in the paper. Pros and cons of the different methods are given before suggesting recommendations.Les calculs de rentabilité des investissements dans le domaine des infrastructures de transport, fondés sur les analyses coûts/avantages, font intervenir ce qu’on appelle, parfois improprement, le surplus des usagers, qui constitue le plus souvent la majeure partie des avantages du projet étudié. Le calcul de ce bénéfice, ou de cet avantage (surplus), tel qu’il est recommandé en France par les instructions officielles, repose sur des avantages moyens. Or, on sait que cette « moyenne » recouvre en fait une large dispersion des données relatives à chaque usager. Cet article se propose de montrer que l’utilisation des surplus issus de modèles de choix discrets, conduit à des valeurs de bénéfices notablement supérieures à celles déduites des calculs « classiques » quand le coût d’usage du projet est élevé. Des simulations sont présentées dans le cas d’une autoroute à péage. Quelques suggestions méthodologiques sont déduites de ces résultats

Identification by MALDI-TOF mass spectrometry of 17 alpha-bromoacetamidopropylestradiol covalent attachment sites on estrogen receptor alpha.

International audienceMass spectrometry was used to identify the sites of covalent attachment of [(14)C]-17alpha-bromoacetamidopropylestradiol ([(14)C]17BAPE(2), an estradiol agonist) to the ligand-binding domain (LBD) of mouse estrogen receptor alpha (ERalpha). A glutathione S-transferase (GST)-LBD chimera protein was overexpressed in Escherichia coli, using a vector encoding GST fused with a C-terminal portion of mouse ERalpha (Ser(313)-Ile(599)), via a sequence enclosing a thrombin cleavage site (located 14 amino acids ahead of Ser313). [(14)C]17BAPE(2) covalent labeling experiments were carried out on the GST-LBD chimera immobilized on glutathione-Sepharose. After thrombin cleavage of the chimeric LBD, two major [(14)C]17BAPE(2)-labeled species of 34 ( approximately 75%) and 30 kDa ( approximately 25%) were detected by SDS-PAGE and autoradiography. Their identity was assessed by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS): two main signals were consistent with the mass of the full-length (Ser(313)-Ile(599)) and truncated LBD (Ser(313)-Ala(573)), both comprising the extra 14 N-terminal amino acids and covalently bound [(14)C]17BAPE(2) (via HBr elimination). A purified (14)C-labeled LBD preparation was trypsinized to identify the covalent attachment sites of 17BAPE(2). HPLC of tryptic fragments only revealed two discrete and practically equivalent radioactive fractions. MALDI-TOF MS analysis of these two fractions showed only two signals which exactly matched the molecular masses of the [(14)C]17BAPE(2)-alkylated Cys(534)Lys(535) and Cys(421)-Arg(438) peptides, respectively. Hydrolysis of the second (14)C-labeled fraction by Staphylococcus aureus V8 Glu-C endoproteinase generated signals typical of alkylated the Cys(421)-Glu(423) tripeptide. We concluded that Cys421 and Cys534 were equivalent alternative covalent attachment sites of 17BAPE(2) on the LBD. These biochemical data were interpreted using the crystallographic structures of estradiol-LBD and raloxifene- or 4-hydroxytamoxifen-LBD complexes. The covalent attachment to Cys421, Cys534, or both could be interpreted according to the starting structure. Various hypotheses based on the biochemical results and molecular modeling simulations are discussed, with the likely involvement of dynamic interconversion between multiple conformational states of the LBD-17BAPE(2) complex